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1
Yang, Weigang. « Electric field control of magnetic properties in multiferroic heterostructures ». Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/13425/.
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Recently, the use of an electric field (E-field) to control the magnetic properties of thin magnetic films has drawn intensive interest due to their important potential applications such as magnetoelectric random access memory (MERAM) devices and magnetoelectric (ME) sensor. In this thesis, the work first includes a study of the strain-mediated ME coupling strength manipulation by either changing ferromagnetic layer thickness (30-100 nm) or inserting a thin Ti buffer layer (0-10 nm). A large remanence ratio (Mr/Ms) tunability of 95% has been demonstrated in the 65 nm CoFe/PMN-PT heterostructure, corresponding to a giant ME constant (α) of 2.5 × 10-6 s/m, when an external E-field of 9 kV/cm was applied. Also, a record high remanence ratio (Mr/Ms) tunability of 100% has been demonstrated in the 50 nm CoFe/8 nm Ti/PMN-PT heterostructure, corresponding to a large ME constant α of 2.1 × 10-6 s/m, when the E-field of 16 kV/cm was applied. Furthermore, the E-field induced magnetic response was repeatable and quick even after 30 repeats were made. Secondly, a study of non-volatile magnetization change has been demonstrated in the 65 nm CoFe/24 nm Metglas/PMN-PT. In this heterostructure, the E-field created two new non-volatile remanence states, although the as-grown magnetic anisotropy was altered permanently, when the E-field between -6 kV/cm to +6 kV/cm was applied. Based on giant magnetoresistance (GMR) or anisotropic magnetoresistance (AMR), the MERAM memory cell was proposed for the fast, low-power and high-density information storage.
2
Blouzon, Camille. « Photoelectric and magnetic properties of multiferroic domain walls in BiFeO3 ». Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066006/document.
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De tous les matériaux multiferroïques, BiFeO3 est celui qui est le plus étudié. C’est un ferroélectrique, antiferromagnétique dont les températures de transition sont bien au-dessus de la température ambiante. De plus, le couplage magnétoélectrique entre ces deux paramètres d’ordre a été observé aussi bien dans les cristaux que dans les couches minces. BiFeO3 possède également la plus grande polarisation ferroélectrique jamais mesurée, 100µC/cm². De gros efforts sont fournis pour comprendre et exploiter les propriétés physiques de ce matériau. Dans ce but, il est important de pouvoir contrôler sa structure en domaines afin d’étudier les phénomènes émergeant aux parois de ces domaines. C’est l’objectif de cette thèse : étudier quelques une des propriétés de BiFeO3, comme la photoélectricité et le magnétisme, tout en prêtant en parallèle une attention particulière à la caractérisation de ces propriétés, dans un domaine et dans une paroi, avec des techniques originales telles que la microscopie de photocourants à balayage (MPB) et le rayonnement synchrotron ou les champs magnétiques intenses. Les images obtenues par MPB, révèlent qu’un champ dépolarisant proche d’une paroi de domaine à 180° peut améliorer de manière significative le rendement des effets photoélectriques : les parois de domaines peuvent être générées et positionnées dans le but de contrôler localement le rendement de l’effet photoélectrique. De plus, l’imagerie de la figure de diffraction de surface d’un réseau de parois de domaines dans des couches minces, par diffusion magnétique résonante de rayons X, permet de montrer que les parois de domaines entraînent la formation de structures magnétiques particulières qui pourraient donner lieu à une aimantationAmong all multiferroics, BiFeO3 is a material of choice because its two ordering temperatures are well above 300K. It is a ferroelectric antiferromagnet, and magnetoelectric coupling has been demonstrated in bulk and in thin films. Remarkably, BiFeO3 has the largest polarization of all known ferroelectrics (100µC/cm²). A huge research effort is carried out worldwide to understand and exploit the physical properties of this material which requires to design and tailor BiFeO3 on many scales. In this sense, developing methods and tools to control the domain structure is essential to explore new emergent phenomena arising at domain walls. This is the aim of the present PhD work. Some of the original properties of BiFeO3 have been investigated including its photoelectric and magnetic properties. A particular attention is given to characterize in a parallel fashion bulk properties and domain walls properties, using original techniques of characterization such as Scanning Photocurrent Microscopy (SPCM), scattering synchrotron facilities or high field pulses. SPCM mapping reveals that depolarizing fields in the vicinity of a 180° domain wall can significantly improve the photovoltaic efficiency. Thus domain walls can be generated and precisely positioned in order to tailor the local photovoltaic efficiency. Moreover, X-ray resonant magnetic scattering on thin films with periodic domain structure shows that domain walls generate specific magnetic structures with possible uncompensated magnetization
3
Thrall, Michael. « The magnetic, electric and structural properties of multiferroic BiFeo3 and BiMnO3 ». Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492716.
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Bulk BiFe03 samples prepared by the conventional mixed oxide route were investigated. High purity Bi203 and Fe203 powders were weighed according to stoichiometry and milled for 20 hours. The powders were pressed into cylinders (10mm diameter by 6mm thickness) at 100 MPa. The cylinders were heated at a rate of 3 degrees C/min at temperatures of between 700 degrees C and 900°C for times between 7.5 minutes and 48 hours. XRD spectra collected from both the as-sintered and 'bulk' (internal) surfaces showed the formation of additional Bi2Fe40, and Bi25Fe04o secondary phases coexisting alongside the main BiFeOs phase.
4
Alqahtani, Mohammed. « Magnetic and magneto-optical properties of doped oxides ». Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3699/.
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This thesis describes the growth, structural characterisation, magnetic and magneto-optics properties of lanthanum strontium manganite (LSMO), GdMnO3 and transition metal (TM)-doped In2O3 thin films grown under different conditions. The SrTiO3 has been chosen as a substrate because its structure is suitable to grow epitaxial LSMO and GdMnO3 films. However, the absorption of SrTiO3 above its band gap at about 3.26 eV is actually a limitation in this study. The LSMO films with 30% Sr, grown on both SrTiO3 and sapphire substrates, exhibit a high Curie temperature (Tc) of 340 K. The magnetic circular dichroism (MCD) intensity follows the magnetisation for LSMO on sapphire; however, the measurements on SrTiO3 were dominated by the birefringence and magneto-optical properties of the substrate. In the GdMnO3 thin films, there are two well-known features in the optical spectrum; the charge transfer transition between Mn d states at 2 eV and the band edge transition from the oxygen p band to d states at about 3 eV; these are observed in the MCD. This has been measured at remanence as well as in a magnetic field. The optical absorption at 3 eV is much stronger than at 2 eV, however, the MCD is considerably stronger at 2 eV. The MCD at 2 eV correlates well with the Mn spin ordering and it is very notable that the same structure appears in this spectrum, as is seen in LaMnO3. The results of the investigations of Co and Fe-doped In2O3 thin films show that TM ions in the films are TM2+ and substituted for In3+. The room temperature ferromagnetism observed in TM-doped In2O3 is due to the polarised electrons in localised donor states associated with oxygen vacancies. The formation of Fe3O4 nanoparticles in some Fe-doped films is due the fact that TM-doped In2O3 thin films are extremely sensitive to the growth method and processing condition. However, the origin of the magnetisation in these films is due to both the Fe-doped host matrix and also to the nanoparticles of Fe3O4
5
Akamatsu, Hirofumi. « Magnetic Properties of Amorphous Oxides and Related Materials ». 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/77993.
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Zong, Yanhua. « Magnetic and magnetodielectric properties of Eu2+-containing oxides ». 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/126809.
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7
Harrison, W. T. A. « Structural and magnetic properties of some mixed metal oxides ». Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379947.
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Hill, Adrian H. « Magnetic properties of mesoporous and nano-particulate metal oxides ». Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3531.
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The magnetic properties of the first row transition metal oxides are wide and varied and have been studied extensively since the 1930’s. Observations that the magnetic properties of these material types change with the dimension of the sample have stimulated many theoretical and experimental studies of the systems involved. As sample sizes decrease towards the nanoscale long range crystallographic order is no longer possible. However, the application of mesoporous silica samples as hard exo-templates to direct the formation of mesoporous metal oxides has provided a new opportunity to explore the influence of scale of crystallographic order further. These types of samples have pore systems running through the material on the mesoscale (diameter between 2nm to 50nm) with pore walls truly in the nanoscale region (7nm to 9nm thick) crystallographically ordered over large scale distances. The work presented in this thesis presents magnetic and crystallographic studies of a variety of the first row transition metal oxides from chromium to nickel in three dimensional mesoporous forms predominantly using SQUID magnetometry and neutron powder diffraction. Rietveld refinements of diffraction data from hematite and eskolaite (®-Fe2O3 and Cr2O3) show that the samples have space groups identical to their bulk counterparts, however slight differences in lattice parameters are observed. Refinement of magnetic properties has also been performed and compared to magnetic property measurements. Of particular interest are results from a mesoporous hematite which show suppression of a well defined first-order magnetic phase transition (the Morin transition). This suppression has been studied extensively with neutron powder diffraction and preliminary inelastic neutron spectroscopic measurements. Comparisons with hematite nanoparticles which also show the suppression of the Morin transition can be drawn. Parametric neutron powder diffraction studies on Co3O4 and NiO samples shows that the Néel ordering temperatures are lowered as the mesoporous structure is imposed. This too was observed in eskolaite. Other studies have been carried out on mesoporous alpha-MnO2 (magnetometry) and nanoscale Li1+xMn2–xO4 (X-ray photo electron spectroscopy) with comparisons to their bulk counterparts and finally nanoparticulate hausmannite Mn3O4 (magnetometry and muon spin relaxation) which exhibits spin-glass type behaviour.
9
Chung, Emma Ming Lin. « Novel magnetic properties of d-electron single crystal oxides ». Thesis, University of Warwick, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269072.
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Knee, Christopher Sebastian. « Synthesis, structure and magnetic properties of complex metal oxides ». Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299519.
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Gallacher, Derek Graham. « Nature and properties of some magnetic mixed metal oxides ». Thesis, Glasgow Caledonian University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371402.
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Tseggai, Mehreteab. « Synthesis, Nuclear Structure, and Magnetic Properties of some Perovskite Oxides ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4826.
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Lappas, C. Alexandros. « Physical properties of magnetic and (super)conducting layered copper oxides ». Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336099.
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Church, Nathan Stewart. « Magnetic properties of iron-titanium oxides and their nanoscale intergrowths ». Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609524.
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Zhang, Lei. « Computational exploration of low-dimensional materials with novel electronic and ferroic/multiferroic properties ». Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232641/1/Lei_Zhang_Thesis.pdf.
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Low-dimensional materials with novel electronic and ferroic properties play a crucial role in the development of next-generation nanoscale functional devices and have drawn extensive research attentions. By using state-of-art first-principles calculations, Monte Carlo simulations, and structural revolution algorithms, four new low-dimensional materials were predicted showing promising applications in electronics or spintronics and two strategies were proposed to introduce ferroelectricity and realize strong electromagnetic coupling in experimentally fabricated low-dimensional materials, which may accelerate the discovery and design of novel functional low-dimensional materials.
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Yourdkhani, Amin. « Synthesis and Characterization of Ferroic and Multiferroic Nanostructures by Liquid Phase Deposition ». ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1579.
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Das, R. « Particle size and morphology dependent magnetic properties of rare-earth manganites with potential multiferroic property ». Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2014. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/1953.
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Nakatsuka, Yuko. « Magnetic and Magneto-optical Properties of Transition Element-containing Amorphous Oxides ». 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225611.
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Baskar, Dinesh. « High temperature magnetic properties of transition metal oxides with perovskite structure / ». Thesis, Connect to this title online ; UW restricted, 2008. http://hdl.handle.net/1773/9812.
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Mukherjee, Paromita. « Investigation of the magnetic and magnetocaloric properties of complex lanthanide oxides ». Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275425.
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Complex lanthanide oxide systems are known to host novel phases of matter, while also providing functionality for practical applications. In this dissertation, the structural, magnetic and magnetocaloric properties of three families of lanthanide oxides have been studied with the dual aims of investigating the magnetic behaviour and identifying promising magnetic refrigerants for cooling to temperatures currently accessible using non-renewable liquid He. The thesis presents a two-part study of the magnetic and magnetocaloric properties of the geometrically frustrated lanthanide garnets, where the magnetic $Ln^{3+}$ form corner-sharing triangles. First, the family of garnets $Ln_3A_2X_3$O$_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Ga, Sc, In, Te, $X$ = Ga, Al, Li are investigated. Changes to the single-ion anisotropy of the magnetic ion as well as variations in the chemical pressure radically alters the nature of magnetic ordering, the degree of frustration and the magnetocaloric performance. In the second part, the garnets $Ln_3A$Ga$_4$O$_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Cr, Mn, are studied. Introducing additional spins significantly reduces the frustration in the garnet lattice. Low temperature powder neutron diffraction of Ho$_3$MnGa$_4$O$_{12}$ reveals concomitant ordering of Ho$^{3+}$ and Mn$^{3+}$ moments below the ordering temperature, $T_N$ = 5.8 K. The magnetocaloric performance of $Ln$_3CrGa$_4$O$_{12}$, $Ln$ = Gd, Dy, Ho, greatly surpasses that of the parent $Ln_3$Ga$_5$O$_{12}$ at $T$ = 2 K. The final results chapters in the thesis describe the magnetism and magnetocaloric effect in the lanthanide orthoborates, $Ln$BO$_3$ , $Ln$ = Eu, Gd, Tb, Dy, Ho, Er, Yb and the lanthanide metaborates, $Ln$(BO$_2$)$_3$, $Ln$ = Pr, Nd, Gd, Tb. The magnetic $Ln^{3+}$ form slightly distorted edge-sharing triangular layers in $Ln$BO$_3$. Unique magnetic features are observed, including short-range ordering and spin reorientation transitions depending on the single-ion anisotropy of the $Ln^{3+}$. The $Ln$BO$_3$ are also efficient magnetocalorics in the liquid helium temperature range. The lanthanide metaborates contain one-dimensional chains of magnetic lanthanide ions. Bulk magnetic measurements show features consistent with low-dimensional magnetism, such as magnetisation plateaux at one-third of the saturation magnetisation for Nd(BO$_2$)$_3$ and Tb(BO$_2$)$_3$ in a field of 14 T. This thesis provides insight into the fundamental magnetic properties of complex lanthanide oxide systems and also demonstrates strategies for identifying new magnetocaloric materials: both through chemical control of the structure of well-known magnetocalorics and by studying materials that have not been explored previously. The results pave the way for further in-depth investigations and finding new magnetic coolants based on complex lanthanide oxide systems.
21
Erten, Onur. « Electronic and Magnetic Properties of Double Perovskites and Oxide Interfaces ». The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1376496346.
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Kususe, Yoshiro. « Synthesis, Structure, and Properties of Eu2+-containing Perovskite Oxides ». 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199320.
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Taylor, Anthony Park 1963. « Terbium iron cobalt diffusion barrier studies ». Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276931.
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Thin films (5nm ± 2nm thick) of ZrO2, Al2O3, TiO2, Sm, Gd, Zr, Ni, and Pt were deposited onto TbFeCo films (100nm ± 20nm thick) on silicon and graphite substrates and analyzed with XPS as prospective candidates for TbFeCo diffusion barriers. Metals were chosen primarily according to electronegativity. Samples were typically heated to 272°C in UHV for 20 hours to enhance diffusion. Experiments with the metals were performed in a more consistent manner than with the oxides. The Sm, Gd, and Zr were reactively oxidized during the deposition. The Sm/Sm-oxide and Gd/Gd-oxide appeared to be favorable candidates for TbFeCo diffusion barriers. TbFeCo was not detected near the surface before or after heating the samples to 272°C for 20 hours and depth profiles indicated oxygen contamination decreased steadily as the barrier/TbFeCo interface was approached. For the other materials examined, either the oxides were reduced (at least partially) during heating to 272°C (381°C for Al₂O₃) or diffusion of TbFeCo was detected after heating, indicating that they would not be favorable candidates for TbFeCo diffusion barriers.
24
Kitada, Atsushi. « Magnetic and Electrical Properties of Transition Metal Oxides Obtained using Structurally Related Precursors ». 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157604.
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Kawamoto, Takahiro. « Synthesis and Structural Analysis of Metastable Transition Metal Oxides with Unique Magnetic Properties ». 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215553.
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Xiong, Jie. « Investigation of Structural and Magnetic Properties of Perovskite Type Oxides Containing 5d Ions ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492623459123207.
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Joseph, J. V. L. « Synthesis, characterization and magnetic properties of substituted perovskite - type manganates and related oxides ». Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2004. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2907.
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Galdi, Alice. « Magnetic orbital and transport properties in LaMnO3 based based heterostructures ». Doctoral thesis, Universita degli studi di Salerno, 2011. http://hdl.handle.net/10556/177.
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2009 - 2010This thesis work deals with the magnetic, orbital and transport properties of (LaMnO3)2N(SrMnO3)N digital superlattices and of LaxMnO3-d thin films, both deposited by molecular beam epitaxy (MBE) technique on SrTiO3 substrates. The (LaMnO3)2N(SrMnO3)N digital superlattices represent the new kind of heterostructure, actually under intensive study, composed by an integer number of unit cells, where electronic reconstruction effects at the (clean) interface are expected. In the first part of the thesis work, optical lithography techniques and different deposition techniques are employed in order to perform transport measurement in current perpendicular to plane (CPP) configuration and field effect measurements. The CPP technique would allow to gain more information respect to the in-plane measurements as the ones used in the first part of the thesis. Field effect has been widely investigated in manganite (especially LMO-based) systems, as it represents a method to tune the carrier density, and in order to engineer all oxide field effect devices. The results of the optimization of such techniques, together with the optimization of the materials needed as base electrode, side and gate insulators and top electrode is reported. In the second part of the thesis, both LaMnO3-based systems were studied by traditional techniques (transport measurements, SQUID magnetometer) and soft X-ray absorption and emission techniques by synchrotron radiation. Collecting the data from different measurement techniques, precious information about ferromagnetism, antiferromagnetism and orbital ordering is obtained. [edited by author]
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Wikberg, Magnus. « Fundamental Properties of Functional Magnetic Materials ». Doctoral thesis, Uppsala universitet, Teknisk-naturvetenskapliga fakulteten, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-133257.
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Magnetic properties of powders, thin films and single crystals have been investigated using magnetometry methods. This thesis provides analysis and conclusions that are supported by the results obtained from spectroscopic and diffraction measurements as well as from theoretical calculations. First, the magnetic behavior of transition metal (TM) doped ZnO with respect to doping, growth conditions and post annealing has been studied. Our findings indicate that the magnetic behavior stems from small clusters or precipitates of the dopant, with ferromagnetic or antiferromagnetic interactions. At the lowest dopant concentrations, the estimated cluster sizes are too small for high resolution imaging. Still, the clusters may be sufficiently large to generate a finite spontaneous magnetization even at room temperature and could easily be misinterpreted as an intrinsic ferromagnetic state of the TM:ZnO compound. Second, influence of lattice strain on both magnetic moment and anisotropy has been investigated for epitaxial MnAs thin films grown on GaAs substrates. The obtained magnetic moments and anisotropy values are higher than for bulk MnAs. The enhanced values are caused by highly strained local areas that have a stronger dependence on the in-plane axis strain than out-of plane axis strain. Finally, spin glass behavior in Li-layered oxides, used for battery applications, and a double perovskite material has been investigated. For both Li(NiCoMn)O2 and (Sr,La)MnWO6, a mixed-valence of one of the transition metal ions creates competing ferromagnetic and antiferromagnetic interactions resulting in a low temperature three-dimensional (3D) spin glass state. Additionally, Li(NiCoMn)O2 with large cationic mixing exhibits a percolating ferrimagnetic spin order in the high temperature region and coexists with a two-dimensional (2D) frustrated spin state in the mid temperature region. This is one of the rare observations where a dimensional crossover from 2D to 3D spin frustration appears in a reentrant material.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 720
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Hudson, Guy Frederick, et Guy Frederick Hudson. « Surface chemistry of magnetic oxides and ferrites and their interaction with selected components of magnetic inks ». Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184919.
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Studies to compare and elucidate some of the surface chemical characteristics of chromium dioxide and barium ferrite magnetic particles have been performed. These investigations primarily involved using the technique of flow microcalorimetry to look at the interaction of molecular probes (pyridine, 4-nitrophenol) and various components present in a magnetic ink (dispersants and model binder compounds) with the particles. The interactions were measured in terms of heats of adsorption and adsorption density. Ancillary experiments using FTIR and XPS were also performed. Both electrophoretic measurements and calorimetric studies showed that stabilized CrO₂ was less acidic than un-stabilized CrO₂. Similar measurements showed that un-doped barium ferrite was more acidic than Co and Ti doped barium ferrite. The interactions of dispersants and model binder components with barium ferrite were found to be very exothermic; heats of interaction of greater than -20 kcal/mole were not uncommon. Subsequent analysis of barium ferrite particles treated with dispersants and binder compounds using FTIR and XPS suggested that these compounds formed chemical complexes on the surface of the ferrite particles.
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Sivakumar, Vikram. « Electrochemical lithiation and delithiation for control of magnetic properties of nanoscale transition metal oxides ». Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44280.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references (p. 119-124).
Transition metal oxides comprise a fascinating class of materials displaying a variety of magnetic and electronic properties, ranging from half-metallic ferromagnets like CrO2, ferrimagnetic semiconductors like Fey's, and antiferromagnetic insulators like rocksalt-structured FeO. The accessibility of multiple electronic configurations and coordination of cations in these oxides enables the control of magnetism by external stimuli. One such stimulus is the insertion of Li+, as occurs during the discharge cycle of a lithium battery. This can lead to the change in valence and locations of the metal cations within the structure therefore a change in magnetic moment. Fey's and CrO2 are of considerable interest, primarily because they demonstrate room-temperature magnetism and high spin polarization.Previous studies focussed on use of these materials as cathodes and characterization of lithiated compounds made through solid state chemical synthesis or via chemical lithiation. In this work, changes in magnetization and structure of pulsed laser deposition (PLD)-grown Fey's (magnetite) thin films, Fe3O4 nanoparticles, and CrO2 nanoparticles have been investigated upon electrochemical lithiation. The reasonable electrical conductivity of magnetite opens the possibility of modifying the saturation magnetization by inserting Li+ ions into thin films grown on conducting substrates. A substantial decrease in M8 (up to 30%) was observed in PLD-grown thin films. Significantly larger reduction in moment (up to 75%) was observed in commercially available nanoparticles upon addition of 2 moles of Li per formula unit, along with changes in remanence and coercivity. The smaller drop in M8 observed in thin films is attributed to a kinetic effect due to high density and greater diffusion lengths in PLD-grown films.
(cont.) The electrochemical lithiation process has also been applied to needle-shaped particles of chromium dioxide and a model has been proposed to explain the observations. The effects of cycling and discharge-charge rate on these CrO2 particles have been studied. It has been shown that the process may be partially reversible for low Li contents. The effects of increasing the temperature of cycling and decreasing the length of the CrO2 particles have been explored. These changes in magnetic moment may be rendered useful in magnetomechanical or magnetoelectronic applications.
by Vikram Sivakumar.
Ph.D.
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Tanaka, Katsuhisa. « ESR AND MOSSBAUER STUDIES ON STRUCTURE AND MAGNETIC PROPERTIES OF IRON-CONTAINING AMORPHOUS OXIDES ». Kyoto University, 1990. http://hdl.handle.net/2433/74576.
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Deka, S. « Studies on the magnetic and electrical properties of nanosized transition metal oxides and ferrites ». Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2006. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2510.
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Hudl, Matthias. « Magnetic materials with tunable thermal, electrical, and dynamic properties : An experimental study of magnetocaloric, multiferroic, and spin-glass materials ». Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168986.
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This thesis concerns and combines the results of experimental studies of magnetocaloric, multiferroic and spin-glass materials, using SQUID magnetometry as the main characteriza-tion technique. The magnetocaloric effect offers an interesting new technology for cooling and heating applications. The studies of magnetocaloric materials in this thesis are focused on experimen-tal characterization of fundamental magnetic properties of Fe2P-based materials. These are promising magnetocaloric materials with potential industrial use. It is found that the magneto-caloric properties of Fe2P can be optimally tuned by substitution of manganese for iron and silicon for phosphorus. Furthermore, a simple device to measure the magnetocaloric effect in terms of the adiabatic temperature change was constructed. Materials that simultaneously exhibit different types of ferroic order, for example magnetic and electrical order, are rare in nature. Among these multiferroic materials, those in which the ferroelectricity is magnetically-induced, or vice versa the magnetism is electrically-induced, are intensively studied due to a need for new functionalities in future data storage and logic devices. This thesis presents results on two materials: Co3TeO6 and Ba3NbFe3Si2O14, which belong to the group of magnetically-induced ferroelectrics and exhibit strong coupling be-tween the magnetic and the electrical order parameter. Their ordering properties were studied using magnetic and electrical measurement techniques. The coupling between the magnetic and electronic degrees of freedom was investigated using high-field and low-temperature Raman spectroscopy. Spin-glass materials exhibit complex magnetism and disorder. The influence of the spin dimensionality on the low and high magnetic field properties of spin glasses was investigated by studying model Heisenberg, XY and Ising spin-glass systems. Significant differences were found between the non-equilibrium dynamics and the hysteresis behavior of Heisenberg systems compared to those of XY and Ising spin glasses.
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Sabo, Daniel E. « Novel synthesis of metal oxide nanoparticles via the aminolytic method and the investigation of their magnetic properties ». Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50122.
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Metal oxide nanoparticles, both magnetic and nonmagnetic, have a multitude of applications in gas sensors, catalysts and catalyst supports, airborne trapping agents, biomedicines and drug delivery systems, fuel cells, laser diodes, and magnetic microwaves. Over the past decade, an inexpensive, simple, recyclable, and environmentally friendly large, scale synthesis method for the synthesis of these metal oxide nanoparticles has been sought. Many of the current techniques in use today, while good on the small, laboratory bench scale, suffer from drawbacks that make them unsuitable for the industrial scale. The aminolytic method, developed by Dr. Man Han while working for Dr. Zhang, fits industrial scale-up requirements. The aminolytic method involves a reaction between metal carboxylate(s) and oleylamine in a non-coordinating solvent. This system was shown to produce a range of spinel ferrites. Dr. Lisa Vaughan showed that this method can be recycled multiple times without degrading the quality of the produced nanoparticles. The purpose of this thesis is to test the versatility of the aminolytic method in the production of a wide range of metal oxides as well as various core/shell systems. Chapter 2 explores the effect of precursor carboxylates chain length on the aminolytic synthesis of cobalt ferrite, and manganese ferrite nanoparticles. In Chapter 3, a series of CuxMn1-xFe₂O₄, (x ranges from 0.0 to 0.2), nanoparticles were synthesized via the aminolytic method. This series allows for the investigation of the effects of orbital Jahn-Teller distortion as well as orbital angular momentum on the magnetic properties of this ferrite. The quantum couplings of magnetic ions in spinel ferrites govern their magnetic properties and responses. An understanding of the couplings between these metal ions allows for tailoring magnetic properties to obtain the desired response needed for various applications. Chapter 4 investigates the synthesis of MnO and Mn₃O₄ nanoparticles in pure single phase with high monodispersity. To the best of our knowledge, the range of sizes produced for MnO and Mn₃O₄ is the most extensive, and therefore a magnetic study of these systems shows some intriguing size dependent properties. The final part of this chapter investigates the applicability of the aminolytic method for building a MnO shell on a CoFe₂O₄ core. Chapter 5 explores the synthesis of another metal oxide, ZrO₂ in both the cubic and monoclinic phases with no impurities. The use of the aminolytic method here removes the need for dangerous/expensive precursors or equipment and eliminates the need for extensive high temperature heat treatments that destroy monodispersity which is required for most techniques. The creation of a core/shell system between CoFe₂O₄ and ZrO₂ using the aminolytic method was also tested. This core/shell system adds magnetic manipulation which is especially useful for the recovery of zirconia based photocatalyst. Chapter 6 studies the application of the aminolytic method in the synthesis of yttrium iron garnet (YIG) and yttrium iron perovskite (YIP) nanoparticles. Current synthesis techniques used to produce YIG and YIP nanoparticles often requires high temperatures, sensitive to contamination, which could be eliminated through the use of our method
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Spring, Lauren E. « Studies on the synthesis and characterisation of compounds showing colossal magnetoresistance ». Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:dbb9fd94-9030-4e8e-b372-96e60b628001.
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The crystallographic and magnetic properties of manganese oxides belonging to the Ruddlesden Popper (RP) series, described by the formula An+1BnO3n+1, are presented. Compounds having n = 2, 3 and ∞ are discussed in Chapters 3, 4 and 5, respectively, their properties being studied by powder X-ray and neutron diffraction, SQUID magnetometry and magnetotransport measurements. In Chapter 3 (A3B2O7) it is shown that Sr2-xNd1+xMn2O7 (0 ≤ x ≤ 0.5) and Sr2PrMn2O7 exhibit colossal, negative magnetoresistance (CMR) below 150K. The zero field resistivity signal is reduced by 2-3 orders of magnitude in a field of 14T, at ~4.2K. The compounds Sr2HoMn2O7 and Sr2YMn2O7 show no significant magnetoresistance. In contrast to the tetragonal Sr,Nd and Sr,Pr compositions, these compounds show a symmetry lowering to space group P42/mnm, and spin glass freezing on the Mn sublattice at ~20K. Chapter 4 (A4B3O10) focuses on A- and B-cation substitutions in the parent compound Ca4Mn3O10-δ. Substitution of Ca by Sr yields Sr4Mn3O10-δ, an orthorhombic (Cmca) compound, composed of trimers of face sharing octahedra. The magnetic susceptibility of this sample is interpreted in terms of direct and indirect antiferromagnetic (AFM) Mn-Mn exchange interactions. The orthorhombic (Pbca) RP phase Ca3.95La0.05Mn3O10-δ has a magnetic transition at ~114K, suggesting that the antiferromagnetic groundstate, with associated weak ferromagnetism arising through the Dzyaloshinsky-Moriya interaction observed in Ca4Mn3O10-δ, is preserved on introduction of a fraction of La3+ dopant cations. Ca3.95La0.05Mn3O10-δ displays CMR at 4K, with the resistivity signal reduced to 18% of the zero field value, in 14T. B-cation substitution yields Ca4Mn2TiO9.93, an orthorhombic (Pbca) RP phase in which the Mn:Ti cation distribution, deduced from the combined results of anomalous dispersion X-ray experiments and neutron diffraction studies, is 59.8%(2.6):40.2%(2.6) and 70.1%(1.3):29.9%(1.3) across the 4b and 8c octahedral sites, respectively. Neutron diffraction studies at 5K show the presence of only short range magnetic interactions in this insulating material, the resistivity of which is reduced by just 10% at 75K in 14T. Chapter 5 (ABO3 or A2BB'O6) describes the mixed B-cation phases, La2GaMnO6 and Nd2GaMnO6, containing Mn3+, 3d4 cations. Both are cation disordered, orthorhombic (Pnma) materials, and Nd2GaMnO6 exhibits a static, cooperative Jahn-Teller (JT) distortion. La2GaMnO6 contains a relatively higher proportion of dynamic, cooperative JT distortions, and as such exhibits isotropic ferromagnetism at 5OK and 5K (2.80(5)μB per Mn aligned along y at 5K), predicted by the 'quasistatic hypothesis', which describes the correlation between electron spin configurations of neighbouring JT cations. The magnetic structure of Nd2GaMnO6 at 5K and 1.7K is modelled as 'AX FY GZ' for the Mn sublattice, and 'Fγ' for the Nd sublattice, using Bertaut's notation, resulting in competing ferromagnetic and antiferromagnetic superexchange interactions on the Mn sublattice along the [010] direction of the unit cell. Both materials are highly insulating and neither displays CMR, with resistivity values in each being reduced to just 96% of the zero field value at 200K, in a field of 14T.
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Das, Supriyo. « Synthesis and structural, magnetic, thermal, and transport properties of several transition metal oxides and arsenides ». [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3403075.
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Aguesse, Frederic. « Structural, electrical and magnetic properties of CoFe2O4 and BaTiO3 layered nanostructures on conductive metal oxides ». Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9300.
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Multiferroic materials exhibit simultaneously, magnetic and electric order. In a magnetoelectric composite structure, a coupling is induced via an interfacial elastic interaction between magnetostrictive and piezoelectric materials enabling the control of the magnetisation by applying an electric field and vice versa. However, despite the potential of such coupling, experimental limits of theoretical models were observed. This work sheds some light on these limits by focusing the research on the chemistry of nanocomposite CoFe2O4 and BaTiO3, particularly at the interfaces where the coupling predominates. A comparison of the most common conductive oxides, Nb doped SrTiO3 and SrRuO3, was made for the bottom electrode application. The variation of conductive properties in Nb-SrTiO3 thin films at high temperature has been quantified when artificially strained and 60 nm SrRuO3 film was found to be the best bottom electrode choice for room temperature use. Epitaxial growth of magnetic CoFe2O4 was achieved on various metal oxide substrates despite large lattice mismatches. Crystallographic properties and strain evaluation were investigated and a Stranski-Krastanov growth mechanism, arising from the PLD deposition, was predominant. A notable drop of magnetisation was observed depending on the growth template, particularly on BaTiO3 substrates, the piezoelectric counterpart of the magnetoelectric structures. However, an encouraging magnetoelectric coupling induced by thermal phase transition of BaTiO3 was revealed. For BaTiO3, a control of the growth direction was realised by varying the deposition pressure, and the existence of both 180° and 90° ferroelectric domains was observed for films up to 300 nm in thickness. However, both the ferroelectric and piezoelectric properties were reduced in the thin films due to the clamping effect of the substrate. Finally, highly crystalline multilayers of CoFe2O4 and BaTiO3 were prepared on SrRuO3 buffered SrTiO3 substrates. It was found that the degradation of both magnetic and ferroelectric properties was proportional to the increase in the number of interfaces. A thorough microscopic study revealed interdiffusion and chemical instability occurring between CoFe2O4 and BaTiO3 at the interface. This undesired effect was partially recovered by the insertion of an ultra thin layer of SrTiO3, acting as a barrier layer at every interface. This research shows how interfacial chemistry need to be understood to achieve high magnetoelectric coupling in these types of epitaxial engineered structures.
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Mahajan, M. B. « Synthesis and studies on the magnetic properties of nanosized oxides of Co, Ni, Cu and Zn ». Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2014. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/1970.
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Chin, Suk Fun. « Superparamagnetic nanoparticles for biomedical applications ». University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0128.
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[Truncated abstract] In the past decade, the synthesis of superparamagnetic iron oxide nanoparticles (SPIONs) has received considerable attention due to their potential applications in biomedical fields. However, success in size and shape control of the SPIONs has been mostly achieved through organic routes using large quantities of toxic or/and expensive precursors in organic reaction medium at high reaction temperature. This has limited the biomedical applications of SPIONs and therefore, development of a synthetic method under aqueous condition that is reproducible, scalable, environmentally benign, and economically feasible for industrial production is of paramount importance in order to fully realise their practical applications. Spinning Disc Processing (SDP) has been used to synthesise superparamagnetic magnetite (Fe3O4) nanoparticles at room temperature via a modified chemical precipitation method under continuous flow condition and offer a potential alternative to be applied to SPIONs production. SDP has extremely rapid mixing under plug flow conditions, effective heat and mass transfer, allowing high throughput with low wastage solvent efficiency. The synthesis process involves passing ammonia gas over a thin aqueous film of Fe2+/3+ which is introduced through a jet feed close to the centre of a rapidly rotating disc (500-2500 rpm). Synthetic parameters such as precursor concentrations, temperature, flow rate, disc speed, and surface texture influence the particle sizes. ... Magnetic silica microspheres are receiving great attention for possible applications in magnetic targeting drug delivery, bioseparation and enzyme isolation. However, the current available methods for preparation suffer from the setback of low loading of Fe3O4 nanoparticles in the silica microsphere, which result in low magnetic moment, thereby limiting their practical applications. Therefore it is of considerable importance to develop new alternative synthetic methods for fabricating magnetic silica microspheres with high magnetic nanoparticles loading. Superparamagentic Fe3O4 nanoparticles (8-10 nm diameter) and curcumin have been encapsulated in mesoporous silica in a simple multiplestep self assembly approach process with high Fe3O4 nanoparticles loading (37%). The synthesis involves loading of curcumin in the Cetyltrimethylammonium bromide (CTAB) micellar rod in the presence of superparamagnetic Fe3O4 nanoparticles via a parallel synergistic approach. The synthesised magnetic mesoporous silica composite material is stable, superparamagnetic with high saturation magnetisation before and after curcumin leaching experiment. Under physiological pH in phosphate buffer, the curcumin is slowly released over several days. These magnetic mesoporous silica are expected to have great potential as targeted drug delivery systems.
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Popa, Adriana. « Study of the Effect of Nanostructuring on the Magnetic and Electrocatalytic Properties of Metals and Metal Oxides ». Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1427735465.
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Briley, Saebo Karen. « Degradation, Metabolism and Relaxation Properties of Iron Oxide Particles for Magnetic Resonance Imaging ». Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4311.
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Yildirim, Oguz. « Effect of microstructure on the magnetic properties of transition metal implanted TiO2 films ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-198820.
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The combined electronic, optic and magnetic properties of transition metal (TM) implanted ferromagnetic TiO2 is of interest for spintronic applications. The nature of the observed abundant ferromagnetism in such materials has been investigated for more than one and a half decades, yet still no clear explanation for its appearance can be given. In this thesis, the origin of the ferromagnetic order in TM:TiO2 systems is studied by investigating the interplay between structural order, defects and incorporation of implanted ions within the host lattice. The defect properties of the host TiO2 are altered by preparing different microstructures of TiO2 (e.g. amorphous, polycrystalline anatase and epitaxial anatase). The difference in microstructure is also found to influence the incorporation of the implanted ions with the host lattice. The crystallographic incorporation of the implanted TM atoms is found only in crystalline films. Moreover, it is observed that the suppression of the dopant related secondary phases can also be achieved by changing the microstructure. The obtained experimental results are compared with the existing theoretical frameworks, while the most relevant one describing our findings is elucidated. Based on this discussion, we propose an ideal microstructural candidate for a dilute magnetic oxide material based on our resultsDie kombinierten elektrischen, optischen und ferromagnetischen Eigenschaften von TiO2, welches mit einem Übergangsmetall (TM) dotiert wurde, sind für Anwendungen in der Spintronik von hoher Bedeutung. Obwohl dieses Material seit mehr als anderthalb Jahrzehnten untersucht wird, kann derzeit noch keine eindeutige Erklärung für den beobachteten Ferromagnetismus gegeben werden. In dieser Arbeit wird die Ursache für die ferromagnetische Ordnung in TM:TiO2-Systemen untersucht, indem der Zusammenhang von struktureller Ordnung, Defekten und der Einlagerung der implantierten Ionen im Wirtsgitter analysiert wird. Durch die Verwendung unterschiedlicher Mikrostrukturen (z.B. amorphes, polykristalliner Anatas und epitaktischer Anatas) wurden auch die Defekteigenschaften des Wirts-Titanoxid variiert. Dabei zeigte sich ein Einfluss der unterschiedlichen Mikrostrukturen auf die Einlagerung der implantierten Atome in das Wirtsgitter. So konnte die Substitution von Ti-Atomen durch Atome des dotierten Übergangsmetalls nur in kristallinen Filmen beobachtet werden. Weiterhin wurde herausgefunden, dass die vom Dotanden hervorgerufenen Sekundärphasen durch die initiale Mikrostruktur unterdrückt werden können. Die experimentellen Ergebnisse wurden mit aktuellen Theorien verglichen. Zusammenfassend wird ein Überblick über die wichtigsten Ergebnisse gegeben, auf Basis welcher eine optimale Mikrostruktur für ein verdünntes magnetisches Oxid vorgeschlagen wird
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Nguyen, Phuong-Hieu T. « Design, synthesis, crystal structure and magnetic properties of novel osmium-based oxides in ordered rock salt structure type ». Thesis, California State University, Long Beach, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1601918.
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AFM materials with triangular cationic sublattices give rise to geometric magnetic frustration. The goal of this project is to study frustrated systems by designed and synthesis of more frustrated systems. For this purpose, the 5d system of osmium transition metal oxide was chosen. The osmium-based compounds are then successfully synthesized using the conventional solid state method. The crystal structures are then characterized by different techniques such as X-ray diffraction and neutron diffraction. To determine the ordering of the crystal systems, magnetic susceptibility and heat capacity measurements are carried out. By employing the spin dimer analysis, magnetic exchange interactions are calculated. These novel osmium-based ordered rock salt structure type systems are then being compared to similar crystal systems in the text.
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Aeschlimann, Raphaël. « Magnetic and transport properties of rare-earth titanate thin films and heterostructures ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS142.
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Les oxydes de métaux de transitions possèdent une large gamme de fonctionnalités (supraconductivité, magnétisme, ferroélectricité, multiferroicité) découlant de l’interaction d’effets structuraux et de corrélations fortes. De plus, des travaux récents ont mis en lumière une physique propre à leurs interfaces, incluant de la supraconductivité ainsi que de la conductivité classique dans le système bidimensionnel (2DES) créé à l’interface de deux isolants de bande, LaAlO₃ et SrTiO₃. Malgré cela pour couvrir l’immense potentiel des interfaces d’oxydes et leur phases électroniques sans précédent, il est nécessaire de combiner des oxydes plus fortement corrélés. Cette thèse à la croisée des chemins entre la physique des électrons fortement corrélés, du magnétisme et de la spintronique a pour but de combiner les instabilités magnétique et électronique pour créer de nouvelles phases électronique contrôlable par stimulus externe. Pour cela nous nous sommes intéressés à la famille relativement inexplorée des titanates de terres rares dont l’ordre magnétique ferro ou antiferro est contrôlé par la taille de la terre rare. Contrairement aux travaux existants, nous nous somme concentrés sur les membres ferrimagnétiques de la famille et leur intégration dans des 2DES. Cette thèse se développera autour de deux axes principaux. Dans un premier temps nous avons étudié plusieurs membres de la famille des titanates de terres rares sous la forme de couches minces épitaxiées. Nous avons aussi mis en évidence la présence d’une couche morte magnétiquement active à la surface de ces échantillons et expliqué sa présence par une suroxydation des ions titane de la surface. Nous avons aussi étudié la présence inattendue d’un moment orbital porté par le titane dans certains des composés étudiés et l’avons corrélé à leur structure magnétique non-colinéaire en conjonction avec un gradient structural observé en microscopie électronique en transmission. Dans un second temps nous avons combiné DyTiO₃ avec SrTiO₃ pour obtenir une interface conductrice possédant des propriétés de magnetrotransport complexes que nous avons interprété avec l’aide d’un modèle faisant intervenir le couplage spin-orbite ainsi qu’un magnétisme induitTransition metal oxides possess a broad range of functionalities (superconductivity, magnetism, ferroelectricity, multiferroicity) stemming from the interplay between structural effects and electronic correlations. Recent work has revealed exciting physics at their interfaces, including conductivity and superconductivity in the two-dimensional electron system (2DES) that forms at the interface between two band insulators, LaAlO₃ and SrTiO₃. However, to embrace the immense potential of oxide interfaces and unveil unprecedented electronic phases, combining insulators with stronger electronic correlations is necessary. At the crossroad between strongly correlated electron physics, magnetism and spintronics, the present thesis project aims to harness electronic and magnetic instabilities in correlated oxides to craft new electronic phases controllable by external stimuli. We investigated rareearth titanates RTiO₃, a relatively unexplored family of Mott insulating perovskites with a crossover between antiferromagnetic and ferromagnetic orders upon changing the rare-earth size. Contrary to most previous works, we focused on ferromagnetic compounds, and their integration in 2DES. The thesis developed along two main axes. First, we explored several members of the rare-earth titanates family in epitaxial thin film form. We highlighted the presence of a magnetically active dead layer at the surface of thin films and established its origin as due to the overoxidation of titanium ions. We also studied the presence of an unexpected orbital moment carried by the titanium in some compounds, and discussed it in the light of the non-collinear spin arrangement promoted by the rare-earth orbital moment and of a structural gradient evidenced by transmission electron microscopy. In a second stage, we combined DyTiO₃ with SrTiO₃ to stabilize a conducting interface with puzzling magnetotransport properties that we interpreted with a model involving spin-orbit coupling as well as induced magnetism
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Teggart, Brian Joseph. « Fabrication, characterisation and magneto-optical enhancement of thin film BiGa : Dy iron garnet ». Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287432.
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Zhang, Yan. « Theoretical study of the transition-metal oxides Pb2FeMoO6 and ZrO2 ». Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112209.
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Ces dernières années, les oxydes de métaux de transition ont suscité de grands intérêts du point de vue fondamental et technologique. A cet égard, nous nous concentrons sur deux types d'oxydes : le première, le Perovskite double Pb2FeMoO6, avec un potentiel d'application sur des appareils magnétorésistances et spintroniques ; le deuxième, la zircone ZrO2 avec de excellentes propriétés mécaniques et diélectriques pour être utilisée dans les domaines de matériaux structuraux et fonctionnels. Dans la présente étude, nous utilisons la méthode ab-initio (first-principles calculation) pour étudier les détails des orbites décomposés des structures électroniques et des propriétés magnétiques du Pb2FeMoO6 massif de structure parfaite, massif avec des défauts et en structure de plaque. En même temps, les détails des orbites décomposés des structures électroniques, les propriétés mécaniques, dynamiques et diélectriques de six phases de la ZrO2 (cubique, tétragonale, monoclinique, orthorhombique I (Pbca), orthorhombique II (Pnma) et (Pca21)) ont également été étudiés. D'abord nous allons faire les calculs ab-initio sur les propriétés structurales, électroniques et magnétiques de double pérovskite Pb2FeMoO6 massif avec structure parfaite, massif avec défauts et en structure de plaque. La densité des états orbitaux décomposés montre le champ cristallin octaédrique des six atomes d'oxygène autour de métal de transition (des Fe ou des Mo) et divise les cinq états dégénérés des atomes libres de Fe ou Mo dans un états triplement dégénéré t2g (dxy, dyz et dzx) avec une énergie plus faible et dans un états doublement dégénéré eg (dz2 et dx2-y2) avec une énergie plus élevée. La nature semi-métalliques et les propriétés de transport complètes (100%) de spin de polarisation de Pb2FeMoO6 massif et en structures de plaque reflètent un grand potentiel d’application dans les dispositifs magnéto-résistifs et spintroniques. Le caractère semi-métallique est maintenu pour le composé Pb2FeMoO6 désordonné contenant d’antisites Fe(Mo), de lacunes de VFe, VO ou VPb, alors qu'il disparaît quand les antisites Mo(Fe), les échanges entre Fe-Mo ou les lacunes de VMo sont présents même la concentration de défauts est réduite jusqu'à C = 6,25%. Ainsi, les antisites Mo(Fe), les échanges entre Fe-Mo ou les lacunes de VMo doivent être évités afin de préserver le caractère semi-métallique du composé Pb2FeMoO6 et donc être utilisables dans des dispositifs magnéto-résistifs et spintroniques.Ensuite, basé sur la rigidité élastique constantes individuelle calculée Cij de six phases de ZrO2, les propriétés élastiques et mécaniques des agrégats polycristallins ont été prédits. Nous avons donc examiné le caractère isolant de la phase cubique/tétragonale de ZrO2 sous forme film avec différentes combinaisons et différentes épaisseurs possibles dans des plans avec des faibles indices de Miller [(001), (110) et (111)] (pour la phase cubique) et [(001), (100), (110), (101) et (111)] pour la phase tétragonale. Il se trouve que pour les différentes combinaisons et épaisseurs possibles dans ces trois / cinq plans avec faibles indices de Miller, seulement ZrO2-terminé sous forme d’un film orienté dans le plan (110)/(100) et O-terminé sous forme d’un film orienté (111)/(101) des phases cubique/tétragonale de ZrO2 maintiennent le caractère isolant même les épaisseurs d’empilement est réduit jusqu'à deux et trois couches atomiques. Puisque cubique et tétragonale ZrO2 ont grande anisotropie élastique, comme un exemple, le stress et l'énergie de déformation densité ont été calculées pour tous {hkl} -oriented grains d'un film ZrO2 cubique polycristallinTransition-metal oxides have attracted exceptional research interest in recent years from both fundamental and technological perspectives. In this respect, we focus on two types of oxides, first, the double perovskite, Pb2FeMoO6 for a potential magnetoresistive and spintronics device application, second, zirconia ZrO2 with great mechanical and dielectric properties can be widely used in both structural and functional material fields. In this thesis we use first-principles calculations (ab-initio) to study systematically the detailed orbital-decomposed electronic structures and magnetic properties of Pb2FeMoO6 in the perfected bulk, defected bulk and slab structures. The detailed orbital-decomposed electronic structures, the mechanical, dynamical and dielectric properties of the ZrO2 in six phases (cubic, tetragonal, monoclinic, orthoI (Pbca), orthoII (Pnma) and (Pca21)) have also been studied.Firstly, considering the comparable ionic radius of Pb2+ (1.49Å) with that of Sr2+ (1.44Å), we propose for the first time to substitute Sr2+ ion with Pb2+ ion in Sr2FeMoO6 and a detailed study has been performed on the Pb2FeMoO6 in the perfected bulk, defected bulk and slab structures. The half-metallic nature and a complete (100%) spin-polarized transport properties reflect the bulk and especially slab Pb2FeMoO6 a potential application in magnetoresistive and spintronics devices; The detailed orbital-decomposed density of states show the octahedral crystal-field of the six oxygen atoms around transition-metal Fe or Mo atoms splits the five-fold degenerate states of the free Fe or Mo atoms into triply degenerate t2g (dxy, dyz and dzx) states with lower energy and doubly degenerate eg (dz2 and dx2-y2) states with higher energy, which cannot be observed in previous partial density of states ( ); The Fe3+ and Mo5+ ions are in the (3d5, s=5/2) and (4d1, s=1/2) states with positive and negative magnetic moments respectively and thus antiferromagnetic coupling via oxygen between them; The half-metallic character is maintained for the disordered Pb2FeMoO6 compounds containing FeMo antisite, VFe, VO, or VPb vacancy, while it vanishes when MoFe antisite, Fe-Mo interchange or VMo vacancy are presented even the defect concentration reduce down to C=6.25%. So the MoFe antisite, Fe-Mo interchange or VMo vacancy defects have to be avoided in order to preserve the half-metallic character of the Pb2FeMoO6 compounds and thus usable in magnetoresistive and spintronics devices.Secondly, based on the calculated individual elastic stiffness constants Cij of six ZrO2 phases, the elastic and mechanical properties of the polycrystalline aggregates have been predicted. We further exam the insulating characters of the cubic/tetragonal ZrO2 slabs with various possible terminations and thicknesses within three [(001), (110) and (111)]/five [(001), (100), (110), (101) and (111)] lower index Miller planes. It is found for the first time that among various possible terminations and thicknesses within these three/five lower index Miller planes, only ZrO2-terminated slabs of the (110)/(100) Miller plane and O-terminated slabs of the (111)/(101) Miller plane of cubic/tetragonal ZrO2 maintain the insulating character and thus usable as a gate dielectric oxide in IC industry even the slab thicknesses reduce down to 2 and 3 atomic layers, respectively; Since cubic and tetragonal ZrO2 have larger elastic anisotropy, both stress and strain energy density have been calculated for all {hkl}-oriented grains of a cubic ZrO2 polycrystalline film as one example
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Ebdah, Mohammad A. « Engineering of the Optical, Structural, Electrical, and Magnetic Properties of Oxides and Nitrides of In-Ga-Zn Thin Films Using Nanotechnology ». Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1305141588.
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Morber, Jenny Ruth. « 1D nanowires understanding growth and properties as steps toward biomedical and electrical application / ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24825.
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Thesis (Ph.D.)--Materials Science and Engineering, Georgia Institute of Technology, 2009.Committee Chair: Snyder, Robert; Committee Co-Chair: Wang, Zhong Lin; Committee Member: El-Sayed, Mostafa; Committee Member: Milam, Valeria; Committee Member: Summers, Christopher; Committee Member: Wong, C. P.
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Takami, T., et H. Ikuta. « Magnetic and thermoelectric properties of quasi-one-dimensional oxides An+_2CoB_nO_3n+_3 (A=Ca,Sr, B=Co,Rh,Ir ; n=1–3) ». American Institite of Physics, 2008. http://hdl.handle.net/2237/11987.
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