Academic literature on the topic 'Nano-magnetism'

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Journal articles on the topic "Nano-magnetism"

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Gibbs, M. R. J. "Nano-Scale Magnetism." Materials Technology 19, no. 2 (January 2004): 98–101. http://dx.doi.org/10.1080/10667857.2004.11753071.

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Liu, Rui Cui, Fu Yi Jiang, and Zi Quan Liu. "Study on the Preparation of Nano Fe3O4 Powder and its Properties." Applied Mechanics and Materials 178-181 (May 2012): 562–65. http://dx.doi.org/10.4028/www.scientific.net/amm.178-181.562.

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The experiment used iron chloride, iron dichloride and other agents as the main resources to prepare the nano Fe3O4 powder by co-precipitation method. Magnets were used to test the magnetism of the prepared nano Fe3O4 powder samples. And the photo-catalytic degradation of rhodamine B solution was used as the model reaction to test the photo-catalytic activity of the prepared nano Fe3O4 powder. The results showed that the prepared nano Fe3O4 powder samples had good magnetism but low photo-catalytic activity.
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Ota, N., N. Gorjizadeh, and Y. Kawazoe. "Magnetism of Edge Modified Nano-graphene." Journal of the Magnetics Society of Japan 36, no. 1_2 (2012): 36–41. http://dx.doi.org/10.3379/msjmag.1108m002.

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Niitaka, Seiji, Kazuyoshi Yoshimura, Atsushi Ikawa, and Koji Kosuge. "Magnetism of Na2V3O7with Nano-Tube Structure." Journal of the Physical Society of Japan 71, Suppl (January 2002): 208–10. http://dx.doi.org/10.1143/jpsjs.71s.208.

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Lisfi, A., T. Ren, A. Khachaturyan, and M. Wuttig. "Nano-magnetism of magnetostriction in Fe35Co65." Applied Physics Letters 104, no. 9 (March 3, 2014): 092401. http://dx.doi.org/10.1063/1.4866183.

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Iannotti, Vincenzo, Alessio Adamiano, Giovanni Ausanio, Luciano Lanotte, Giuliana Aquilanti, John Michael David Coey, Marco Lantieri, et al. "Fe-Doping-Induced Magnetism in Nano-Hydroxyapatites." Inorganic Chemistry 56, no. 8 (April 5, 2017): 4446–58. http://dx.doi.org/10.1021/acs.inorgchem.6b03143.

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Kowlgi, Krishna, Lian Zhang, Stephen Picken, and Ger Koper. "Anomalous magnetism in noble metal (nano)particles." Colloids and Surfaces A: Physicochemical and Engineering Aspects 413 (November 2012): 248–51. http://dx.doi.org/10.1016/j.colsurfa.2012.01.023.

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Enoki, Toshiaki, Naoki Kawatsu, Yoshiyuki Shibayama, Hirohiko Sato, Roji Kobori, Satoshi Maruyama, and Katsumi Kaneko. "Magnetism of nano-graphite and its assembly." Polyhedron 20, no. 11-14 (May 2001): 1311–15. http://dx.doi.org/10.1016/s0277-5387(01)00611-8.

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Sobolev, Kirill, Hanna Pazniak, Michael Farle, Valeria Rodionova, and Ulf Wiedwald. "Synthesis, phase purification and magnetic characterization of the (Cr1−x, Mnx)2AlC MAX-phase." Journal of Materials Chemistry C 9, no. 46 (2021): 16516–22. http://dx.doi.org/10.1039/d1tc03092b.

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Prokopenko, O. V., D. A. Bozhko, V. S. Tyberkevych, A. V. Chumak, V. I. Vasyuchka, A. A. Serga, O. Dzyapko, et al. "Recent Trends in Microwave Magnetism and Superconductivity." Ukrainian Journal of Physics 64, no. 10 (November 1, 2019): 888. http://dx.doi.org/10.15407/ujpe64.10.888.

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We review the development trends in microwave magnetism and superconductivity over the last five decades. The review contains the key results of recent studies related to the promising areas of modern magnetism and applied physics – spintronics, magnonics, magnon caloritronics, physics of magnonic crystals, spin-wave logic, and the development of novel micro- and nano-scale magnetic devices. The main achievements in these fields of physics are summarized and generalized.
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Dissertations / Theses on the topic "Nano-magnetism"

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Cook, James. "Optical magnetism with metallic nano-composites." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616915.

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The transmission and effective magnetic properties of a metamaterial consisting of silver nanowires that we call a "silver nanoforest" was investigated using finite element numerical simulations in the optical regime. The variation of these properties with the arrangement and size of the nanowires was also investigated along with resilience to fabrication disorder. The silver nanoforest metamaterial exhibited low loss diamagnetism associated with Fabry Perot interference. In addition to diamagnetism both negative pelmeability and negative refractive index were obtained, but not simultaneously at same' wavelength and geometry. Both negative permeability and negative index experienced significant loss and therefore low transmission due to the plasmonic Origins of these effects. Magnetic responses of the silver nanoforest metamaterial were dampened but not inhibited by disorder, with diamagnetic response being the most resilient magnetic response to disorder.
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Persson, Andreas. "X-ray Absorption Spectroscopy on Nano-Magnet Arrays and Thin Films : Magnetism and Structure." Doctoral thesis, Uppsala universitet, Yt- och gränsskiktsvetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-112824.

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The magnetic and structural properties of nano magnet arrays and ferromagnetic thin films are investigated. Circular x-rays are used and extensive use is made in this Thesis of the X-ray Magnetic Circular Dichroism (XMCD) technique. By means of the XMCD magneto-optic sum rules the values of the orbital and spin moments are determined. In the case of the nano magnet arrays studied, the XMCD technique is used in a spatially resolved mode using Photo Electron Emission Microscopy (PEEM) after circular light excitation. The Extended X-ray Absorption Fine Structure (EXAFS) is studied in both the Co K- and L-edges. In situ Co L-edge X-ray XMCD spectroscopy measurements are presented, in combination with spectro-microscopy results, on Co/Pt and Co/Au based nano-dot arrays, of typical dot lateral size 250×100 nm2, on self organized Si0.5Ge0.5. The Co is only a few atomic layers thick. The dot arrays display a high degree of lateral order and the individual dots, in several cases, exhibit a stable magnetic moment at 300 K. It is found possible to characterize the spin reorientation of these dot arrays. For both systems the in- versus out-of-plane orbital moment anisotropy, is not always related with an out-of-plane magnetization and the occurrence of a spin reorientation. By performing Co K-edge EXAFS measurements the local atomic structure around the Co atoms is characterized. The feasibility of a high precision quantitative structural analysis of L-EXAFS is studied on the system Au/Co/Au/W(110). The spin reorientation transition is studied as a function of the Co thickness and Au cap thickness. The L-edge EXAFS indicates that this reorientation is correlated to a lattice expansion in the perpendicular direction. High precision angle dependent XMCD work is performed on a high temperature exchange bias system. Pinned or frozen magnetic moments are studied within an exchange biased NiFe ferromagnet at the NiFe/FeMn, ferromagnet/antiferromagnet interface by XMCD and complemented by x-ray resonant reflectivity experiments, at the Ni, Fe and Mn L-edges. The Mn L-edge XMCD MnSb and of (Ga, Mn)As layers modified by high temperature annealing is studied. For MnSb an enhanced value is obtained versus theoretical calculations. This result can be explained by means of the enhanced surface to volume ratio for the samples studied. For (Ga, Mn)As differences are found in the local environment of the Mn atoms upon annealing.
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Maurer, Thomas. "Magnetism of anisotropic nano-objects : magnetic and neutron studies of Co1-xNix nanowires." Paris 11, 2009. http://www.theses.fr/2009PA112340.

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Le nanomagnétisme est actuellement un champ d'investigation très actif grâce aux développements de méthodes de synthèse et d'investigation originales. Cette thèse s'attache à sonder le magnétisme de nanofils magnétiques synthétisés par un procédé polyol. Ce procédé présente l'avantage de fournir un large éventail d'objets magnétiques anisotropes présentant une très bonne qualité cristalline. Les nanofils ainsi synthétisés présentent des diamètres variant de 7nm à 20nm, leur conférant un mode de renversement de l'aimantation cohérent. Cette thèse montre que les nanofils ainsi synthétisés ont des coercivités élevées comparées à celles de nanofils synthétisés par d'autres voies. Par ailleurs, les effets de l'oxydation de ces nanofils sur leurs propriétés magnétiques ont été étudiés. Les mesures magnétiques ont révélé une dépendance en température des champs d'échange et coercitif inhabituelle. Cela a permis de mettre en lumière le rôle prépondérant des fluctuations superparamagnétiques des grains antiferromagnétiques d'oxyde de cobalt dans le phénomène d'Exchange Bias. Enfin, cette thèse a aussi pour objectif de développer la technique de Diffusion de Neutrons Polarisés aux Petits Angles pour sonder le magnétisme de nanofils. Jusqu'à présent, cette technique a été surtout réservée à l'étude d'objets magnétiques isotropes. En effet, l'alignement des nanofils est crucial pour extraire des informations quantitatives d'une telle étude. C'est pour cela, qu'outre les nanofils synthétisés par procédé polyol, des nanofils inclus dans des matrices d'alumine poreuse ont aussi été étudiés par cette technique
Magnetism of individual nano-objects is a very active research field thanks to the development of original synthesis routes and investigation tools. This thesis aims at probing the magnetism of nanowires synthesized via a pure chemical route, the polyol process. This process provides a large variety and an excellent crystallinity of the synthesized nanowires. This process allows to tune the diameter of the nanowires from 7nm to 20nm leading to coherent magnetization reversaI in the nanowires. I show how the large shape and magnetocrystalline anisotropies provide large coercivities compared to magnetic nanowires synthesized via other routes. Furthermore, the oxidation of such objects has also been investigated. Magnetic measurements has revealed unsual temperature dependencies of both the coercive and exchange fields, emphasizing the role of the superparamagnetic fluctuations of the CoO antiferromagnetic grains in the Exchange Bias effect. Finally, this thesis also aims at developing Polarized Small Angle Neutron Scattering to probe magnetism in complex nano-objects. Such a technique has been ignored until now to study magnetic anisotropic nano-objects despite being well adapted. The key ingredient to carry through such a study is the perfect alignment of the nanowires. This is why, besides the nanowires synthesized via the polyol process, Polarized Small Angle neutron Scattering measurements have been performed on arrays of magnetic nanowires included in porous alumina membranes
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Lima, Valquiria Fernanda Gonçalves de. "Preparação e caracterização de nanopartículas magnéticas de Sm-Co, Nd-Fe-B, Fe-Pt e Co-Pt pelo método de agregação gasosa." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26112014-135553/.

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Atualmente, nanopartículas (NPs) são utilizadas em todos os ramos da tecnologia. Suas promissoras aplicações envolvem entre outros, o campo dos sensores e transdutores, mídia de gravação magnética, carreadores magnéticos de drogas medicinais. Com o objetivo de produzir NPs pelo método físico, um gerador de nanopartículas foi adaptado usando um dos canhões do sistema de magnetron sputtering, baseando-se no método de agregação gasosa. Com o gerador somos capazes de produzir NPs de diversos materiais e codepositá-las em matrizes dielétricas ou metálicas. Neste trabalho apresentamos o desenvolvimento da metodologia para a produção de nanopartículas de materiais magnéticos duros, usando alvos de SmCo5, Sm2Co17, Nd2Fe17B, FePt e CoPt. Investigamos a influência dos parâmetros de deposição (pressão, fluxo de gás e potência de sputtering), tipo de substrato e a existência de buffer e/ou codeposição, na obtenção das propriedades estruturais e magnéticas desejadas para esses materiais. As NPs produzidas são analisadas magneticamente pelo VSM e SQUID, sua morfologia e tamanho por TEM e SEM, a sua estequiometria pelo RBS, e a sua estrutura cristalina por XRD, a fim de obter nano-ímãs de alta anisotropia magnética. Da caracterização morfológica, através de microscopia eletrônica, encontramos para as NPs produzidas e estudadas diâmetros entre 5 e 17 nm. Através de análises de RBS obtemos para composição das NPs que as mesmas possuem estequiometria diferente dos alvos usados. Estudos estruturais e magnéticos mostram que para Sm-Co, Fe-Pt e Co-Pt é possível obter NPs cristalinas e com coercividade da ordem de 1 kOe.
In the recent years, nanoparticles (NPs) are being in all fields of technology. Their promising applications involve among others, the field of sensors and transducers, magnetic recording media, magnetic carriers of medicinal drugs. Aiming to produce NPs by physical method, a generator of nanoparticles was adapted using a system of guns \"magnetron sputtering\", based on the aggregation gas method. With the generator we are able to produce NPs with different types of material. In this work, we present the development of the methodology for the production of nanoparticles of hard magnetic materials, using targets of SmCo5, Sm2Co17, Nd2Fe17B, FePt and CoPt. We investigated the influence of the deposition parameters (pressure, gas flux and sputtering power), substrate type and the existence of the buffer and/or codeposition layers, to obtain the desired structural and magnetic properties for the nanoparticles. The produced NPs were magnetically analyzed by VSM and SQUID, the morphology and size by TEM and SEM, the stoichiometry by RBS and the crystal structure by XRD. The main objective of this work is to obtain nano-magnet with high magnetic anisotropy. Through the morphological characterization by electron microscopy, we found for NPs produced and studied have diameters between 5 and 17 nm. Through RBS analysis we have obtained the composition of the NPs, and also that they have different stoichiometry in relation to the used targets. Structural and magnetic studies have show that for Sm-Co, Fe-Pt and Co-Pt it is possible to obtain crystalline NPs with coercive field around 1 kOe.
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Lifvenborg, Louise. "Fabrication and characterization of novel nano-magnets." Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-420995.

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Magnetic data storing has been of great interest since 1950 when the first magnetic hard drive was fabricated. A lot has happened since then, but there is still a need for smaller and cheaper devices.  One way to achieve this is by creating nano-sized ferromagnetic areas in a thin film at room temperature, or nano-magnets. In this thesis, the aim is to fabricate and characterize novel amorphous nano-magnets. Using a chromium mask ions can be implanted in a nano-sized pattern in an amorphous iron zirconium thin film. The mask is fabricated by depositing chromium over the iron zirconium and etching the nano-structures into the chromium film.  This requires the parameters for the etching to be optimized. It is discovered the parameters change with the size and shape of the pattern. Magnetization and structural characterization were performed by using the magneto-optical Kerr effect and a magnetic force microscope. The result shows that the nano-magnets become magnetically harder than the reference sample. The study further reveals structural details for further improvements in implanted regions.

Opponent: Stivan Sabir

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Delshadi, Sarah. "Tests de diagnostic immunologique rapides combinant des nanoparticules magnétiques et des micro-aimants structurés." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV070.

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Cette thèse présente le développement de tests immunologiques innovants, rapides et sensibles combinant des nanoparticules superparamagnétiques (SPN) fonctionnalisées et des micro-aimants : nos immuno-essais magnétiques exploitent les forts gradients de champ magnétique de ces micro-aimants pour capturer les complexes immunologiques liés aux SPN. L’attraction magnétique est souvent utilisée en biotechnologies car elle peut générér des forces capables de capturer des molécules d’intérêt. Les immuno-essais sur billes utilisent habituellement des aimants centi- et millimétriques pour capturer des micro-particules. Réduire la taille des particules magnétiques est très intéressant pour réduire les cinétiques de réactions, tout en diminuant les phénomènes de sédimentation et d’agrégation. Cette réduction d’échelle des particules permet aussi d’augmenter la surface de réaction et ainsi d’augmenter la sensibilité des tests. Cependant les aimants millimétriques génèrent des gradients faibles qui capturent difficilement les SPN, trop mobiles. Les micro-aimants de l’Institut Néel génèrent des forts gradients locaux et ainsi des forces magnétiques importantes. Ces technologies innovantes sont utilisées dans cette thèse pour développer des immuno-essais rapides tirant profit de la réduction d’échelle des particules et des aimants, par rapport aux technologies commerciales.Dans un premier temps, nous avons développé un test immunologique magnétique (MagIA) colorimétrique, comme approche innovante du test ELISA. Nous avons réalisé une preuve de concept pour la détection d’anticorps dirigé contre l’ovalbumine et comparé les résultats avec ceux de tests ELISA. Le test MagIA optimisé présente une limite de détection et une zone dynamique similaires au test ELISA développé avec les mêmes réactifs biologiques. Les micro-aimants fabriqués selon la méthode de micro-magnetic imprinting sont intégrés à bas coût dans les micro-puits des plaques multi-puits ELISA, et permettent la capture efficace des complexes immunologiques couplés aux SPN. La méthode est générique est permet de réaliser des tests ELISA en 30 minutes avec le même équipement.Nous avons ensuite développé un test magnétique immunologique avec une détection fluorescente locale tirant profit des propriétés de capture locale des SPN sur les micro-aimants. Ce test permet la quantification de la molécule d’intérêt en à peine 15 minutes sans étape de lavage. Une preuve de concept réalisée sur la détection de l’anticorps anti-ovalbumine a été réalisée, avec des anticorps de détection fluorescents et des micro-aimants fabriqués selon la méthode de thermo-magnetic patterning. La mesure différentielle entre le signal fluorescent provenant des complexes immunologiques couplés aux SPN localisées sur les micro-aimants, et le signal non spécifique (à l’extérieur des micro-aimants) permet la quantification d’une molécule. Ce test MLFIA (magnetically localized FIA) possède des performances jusqu’à 100 fois meilleures que les tests ELISA standard, pour la détection d’anticorps anti-ovalbumine en PBS. Le test MLFIA a ensuite été transféré à la détection de paramètres cliniques tels que la protéine C réactive, l'ostéopontine, et les sérologies de la toxoplasmose (IgG et IgM). La comparaison des résultats avec des méthodes automatisées a montré d’excellentes corrélations. Le test MLFIA présente plusieurs avantages : il est versatile, compatible avec les milieux biologiques, utilise de faibles volumes et requiert peu d’énergie. Ces résultats ouvrent la voie à une nouvelle génération de tests immunologiques sensibles et nous développons désormais un lecteur miniature pour le diagnostic portable
This thesis reports the development of innovative, sensitive and fast immunoassays combining functionalized superparamagnetic nanoparticles (SPN) and micro-magnets. Our magnetic immunoassays exploit high gradients generated by micro-magnets to capture immune-complexes captured on SPN. Magnetic attraction is widely used in biotechnology, because it provides long-range forces able to capture molecules of interest. Bead-based immunoassays use common centimetre-scale magnets to attract micro-particles. Those magnets generate low magnetic gradients and struggle to capture superparamagnetic nano-particles, which are too small and mobile to be efficiently trapped. Down-scaling the size of magnetic particles is very interesting since it allows diffusion-based transport to perform faster reactions, while avoiding particle sedimentation and aggregation. Furthermore, it increases the reaction surface, which improves the sensitivity of immunoassays. Thanks to the scaling law effects micro-magnets from Institut Néel generate high local gradients and therefore large magnetic volume forces: we use this innovative technology to develop fast immuno-assays that take advantage of a radical size reduction, compared to commercial technology.We first developed a colorimetric magnetic immunoassay (MagIA) as a new approach to standard ELISA. A proof-of-concept based on colorimetric quantification of anti-ovalbumin antibody in buffer was performed and compared with conventional ELISAs. After optimization, MagIA exhibits a limit of detection and dynamic range similar to ELISAs developed using the same biochemical tools. Micromagnets made by the micro-magnetic imprinting method can be fully integrated in multi-well plates at low cost, allowing the efficient capture of immuno-complexes carried by SPNs. The method is generic and performs magnetic ELISA in 30 min.We then developed a magnetically localized fluorescent immunoassay (MLFIA) exploiting the local capture of SPN on micro-magnets. The differential measurement of fluorescence localized on and besides micro-magnet arrays allows the detection and quantification of a molecule in only 15 minutes without fluid handling. We present a proof of concept based on the detection of monoclonal antibody anti-ovalbumin. Functionalized nanoparticles are incubated with fluorescent detection antibody and the sample containing the molecule to be detected. After a single incubation step, the nanoparticles are captured on micro-magnets made by thermo-magnetic patterning. Fluorescence is then read under a microscope. Differential measurement between the signal from the immunological complex localised on the micro-magnets and the non-specific signal localised besides micro-magnets allows the quantification of mAb anti-OVA. The performance of MLFIA was compared with conventional ELISA and exhibits a limit of detection up to 100 times better for anti-OVA mAb in PBS. For further validation, MLFIA was used to measure clinical parameters: we developed a sandwich assay to detect C-reactive protein, and a serology for Toxoplasma gondii immunoglobulin G and M or osteopontin in human samples. Comparisons with data obtained with routine clinical automatized methods show excellent correlation. Our MLFIA technology presents several key advantages: it is compatible with biological media (serum, plasma), uses small volumes and requires little energy. It also is versatile and thus can be used to detect any antigen or antibody in complex media. We are currently developing a portable prototype for point-of-care diagnostics. The results will open the way to a new generation of sensitive immunological lab-on-chip
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Panighel, Mirco. "Adsorption, metalation and magnetic properties of tetra phenyl porphyrins on metal surfaces." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/10898.

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2013/2014
Traditional semiconductor technology will reach a size limit within the next few years. A possible solution could be the use of organic molecules in technological applications as single functional units in metal-organic based devices; the success of this approach strongly depends on the understanding of the behaviour of these molecules on metallic surfaces. The interaction with metallic substrates and the interaction between the molecules themselves determine the electronic and magnetic properties of the system, and it is thus of fundamental interest to study these metal-organic interfaces both in the case of single molecules and layer structures. In this thesis, an extensive study of the electronic and magnetic properties of tetra-phenyl-porphyrin (2H-TPP) molecules adsorbed on metal surfaces is reported. By means of scanning tunnelling microscopy (STM) we studied the adsorption geometry of these molecules on the Au(111), Ag(111) and Cu(100) surfaces. By using X-ray photoemission spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, a temperature-induced conformational adaptation reaction of the 2H-TPP molecules adsorbed on the Au(111) and Ag(111) surfaces, upon annealing at 550 K, is described. A possible dehydrogenation reaction, with the formation of new C-C bonds, could explain the rotation of the molecule phenyl rings parallel to the surface plane and the associated increasing in the molecule-substrate interaction. In-situ metalation of porphyrins in ultra-high vacuum is obtained by two methods: in the first one, the metalation of 2H-TPP on Ag(111) is achieved by direct metal evaporation (Mn, Rh and Fe) on the molecular layer; in the second case we report the self-metalation of 2H-TPP through the coordination with a metal atom from the Fe(110) and Al(111) substrates. In addition, we investigated the effects of metalation and temperature-induced conformational adaptation on the molecule-substrate interaction, by means of XPS and NEXAFS, in the case of CoTPP on Ag(111). The magnetic properties resulting from the metal coordination are studied by X-ray magnetic circular dichroism (XMCD). Here, a description of the magnetic coupling of a MnTPPCl single layer with a Fe(110) ferromagnetic substrate is disclosed. Moreover, we focused on the study of the magnetic properties and exchange coupling of two layer of molecule and a ferromagnetic thin film. In the case of a MnTPP layer on FeTPP/Fe(110) the magnetic coupling extends to the second layer of molecules, for which the magnetization is opposite with respect to the substrate.
Le tradizionali tecnologie utilizzate nell’industria dei semiconduttori raggiungeranno, entro breve tempo, il limite nella miniaturizzazione dei loro componenti. Una possibile alternativa potrebbe venire dall’utilizzo di molecole organiche come singole unità funzionali in dispositivi metallo-organici; d’altra parte il successo di questo approccio dipende in maniera sostanziale dalla comprensione del comportamento di queste molecole sulle superfici dei metalli. L’interazione con il substrato metallico e la stessa interazione tra le molecole determinano le proprietà elettroniche e magnetiche di questi sistemi, ed è dunque di fondamentale interesse lo studio di queste interfacce metallo-organiche sia nel caso di singole molecole che di strutture più complesse. In questa tesi è riportato uno studio dettagliato delle proprietà elettroniche e magnetiche di tetra-fenil-porfirine (2H-TPP) adsorbite su superfici metalliche. Attraverso la microscopia a scansione a effetto tunnel (STM) è stata studiata la geometria di adsorbimento di queste molecole sulle superfici Au(111), Ag(111) e Cu(100). Utilizzando le spettroscopie XPS (X-ray photoemission spectroscopy) e NEXAFS (near-edge X-ray absorption fine structure) è descritta la reazione di adattamento conformazionale delle 2H-TPP adsorbite sulle superfici Au(111) e Ag(111) a seguito del processo di annealing a 550 K. Una possibile reazione di de-idrogenazione, con la formazione di nuovi legami C-C, può spiegare la rotazione dei gruppi fenili della molecola verso la superficie e l’aumento dell’interazione molecola-substrato ad esso associato. La metallazione in-situ delle porfirine in ultra-alto vuoto è ottenuta in due modi: nel primo, la metallazione delle 2H-TPP su Ag(111) è raggiunta con la diretta evaporazione del metallo (Mn, Rh e Fe) sullo strato di molecole; nel secondo caso, sulle superfici Fe(110) e Al(111) la metallazione avviene automaticamente tramite la coordinazione della 2H-TPP con un atomo della superficie. Inoltre, gli effetti della metallazione e dell’adattamento conformazionale sull’interazione molecola-substrato sono stati studiati, tramite XPS e NEXAFS, nel caso di CoTPP su Ag(111). Le proprietà magnetiche risultanti dalla coordinazione della molecola con un atomo metallico sono state studiate per mezzo della tecnica XMCD (X-ray magnetic circular dichroism). In particolare, viene descritto l’accoppiamento magnetico di un singolo strato di MnTPPCl con un substrato ferromagnetico Fe(110). Inoltre, ci si è focalizzati sullo studio delle proprietà magnetiche tra due strati di molecole e un film sottile ferromagnetico. Nel caso specifico di MnTPP su FeTPP/Fe(110) l’accoppiamento magnetico si estende al secondo strato di molecole, per il quale la magnetizzazione è opposta rispetto al substrato.
XXVII Ciclo
1986
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Bonetti, Stefano. "Magnetization Dynamics in Nano-Contact Spin Torque Oscillators : Solitonic bullets and propagating spin waves." Doctoral thesis, KTH, Materialfysik, MF, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26955.

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Magnetization dynamics in nano-contact spin torque oscillators (STOs) is investigated from an experimental and theoretical point of view. The fundamentals of magnetization dynamics due to spin transfer torque are given. A custom-made high frequency (up to 46 GHz) in large magnetic fields (up to 2.2 T) microwave characterization setup has been built for the purpose and described in this thesis. A unique feature of this setup is the capability of applying magnetic fields at any direction θe out of the sample plane, and with high precision. This is particularly important, because the (average) out-of-plane angle of the STO free magnetic layer has fundamental impact on spin wave generation and STO operation. By observing the spin wave spectral emission as a function of θe, we find that at angles θe below a certain critical angle θcr, two distinct spin wave modes can be excited: a propagating mode, and a localized mode of solitonic character (so called spin wave bullet). The experimental frequency, current threshold and frequency tuneability with current of the two modes can be described qualitatively by analytical models and quantitatively by numerical simulations. We are also able to understand the importance, so far underestimated, of the Oersted field in the dynamics of nano-contact STOs. In particular, we show that the Oersted field strongly affects the current tuneability of the propagating mode at subcritical angles, and it is also the fundamental cause of the mode hopping observed in the time-domain. This mode hopping has been observed both experimentally using a state-of-the-art real-time oscilloscope and corroborated by micromagnetic simulations. Micromagnetic simulations also reveal details of the spatial distribution of the spin wave excitations. By investigating the emitted power as a function of θe, we observed two characteristic behaviors for the two spin wave modes: a monotonic increase of the power for increasing out-of-plane angles in the case of the propagating mode; an increase towards a maximum power followed by a drop of it at the critical angle for the localized mode. Both behaviors are reproduced by micromagnetic simulations. The agreement with the simulations offers also a way to better understand the precession dynamics, since the emitted power is strongly connected to the angular variation of the giant magnetoresistance signal. We also find that the injection locking of spin wave modes with a microwave source has a strong dependence on θe, and reaches a maximum locking strength at perpendicular angles. We are able to describe these results in the theoretical framework of non-linear spin wave dynamics.
QC 20101130
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Sá, Artur Domingues Tavares de 1985. "Nano-agregados metálicos = produção e propriedades magnéticas." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/276993.

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Orientador: Varlei Rodrigues
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Clusters, i.e. nanopartículas formadas por alguns átomos ou até 107, atraem grande interesse devido 'as propriedades peculiares que apresentam, como momento magnético aumentado, atividade catalítica, fluorescência dependente de tamanho e estruturas geométricas diferenciadas em relação ao material massivo. Isso acontece principalmente devido aos efeitos decorrentes da grande razão entre o número de átomos na superfície e o número de átomos no volume, e também por conta dos níveis discretos de energia devidos ao pequeno número de átomos presente nas estruturas. Entretanto, para que seja possível uma melhor compreensão dos mecanismos envolvidos em amostras compostas por clusters, 'e imprescindível que tenhamos um grande controle dos parâmetros cruciais como tamanho das partículas, concentração e energia de deposição. Para isso, desenvolvemos e construímos uma fonte para a produção de agregados com um número controlável de átomos, com a intenção de produzir partículas com 2 até 100 átomos. Um feixe de partículas 'e produzido, caracterizado e depositado em condições de ultra alto vácuo (UHV), utilizando-se uma fonte de clusters com magnéton sputtering. A fonte 'e baseada na proposta por Haberland et al. (1) com a inovadora introdução de um sputtering com geometria cilíndrica, com a intenção de aumentar a eficiência na criação de partículas bem como facilitar a produção de agregados de ligas. Uma fonte de clusters geralmente é constituída essencialmente de: uma fonte de átomos e uma câmara de agregação, para gerar as partículas; um sistema de lentes eletrostáticas, para guiar e focalizar o feixe; e um analisador de massa, podendo esse selecionar, ou não, as partículas em massa. Para fonte de átomos desenvolvemos dois magnéton sputterings, um magnéton circular plano típico de 1" e um magnéton cilíndrico para a erosão axial de fios metálicos. A câmara de agregação tem um comprimento variável (0-300 mm), para que possamos controlar o tamanho médio dos nano-agregados. Um skimmer, três lentes Einzel e uma Bessel-Box são utilizadas para guiar e focalizar o feixe de partículas ao longo do instrumento. Como analisador de massa, construímos um espectrômetro de massa por tempo de voo. É importante frisar que optamos por desenvolver a maioria dos componentes na própria Unicamp, estes componentes serão descritos no corpo dessa tese. O equipamento que se encontra operacional, já se mostrou capaz de produzir partículas com mais de 500 átomos, superando assim nossas expectativas iniciais. Apresentamos também a caracterização magnética de nanoestruturas granulares com nano-agregados de cobalto com 2,3 nm de diâmetro embebidos em matrizes de cobre com diferentes concentrações. A comparação dos resultados utilizando-se o triple fit e medidas de transporte mostra que apenas para baixa concentração (0,5 at.% Co) todos os experimentos são consistentes com a suposição de que as partículas são não-interagentes e a descrição teórica comumente utilizada é apropriada. Aumentando-se a concentração para 2,5 at.% e 5 at.% implica em desvios entre magnetometria e magneto-transporte
Abstract: Clusters, i.e. nano-particles formed by a few tens or up to 107 atoms, attract great interest due to their peculiar properties as enhanced magnetic moment and catalytic activity, size-specific fluorescence and non-bulky geometrical structures. This happens mainly due to effects arising from their high surface-to-bulk ratio and because of the discrete energy levels due to the small amount of atoms at these structures. However, in order to get a deeper understanding of the mechanisms taking place in cluster-assembled samples, it is fundamental to have a good control of crucial parameters such as clusters size, composition, concentration and deposition energy. In this way, we have developed and constructed a source to produce clusters with a controllable number of atoms intended to produce particles ranging from 2 up to 100 atoms. A beam of cluster ions is produced, characterized and deposited under ultra high vacuum (UHV) conditions, using a magnetron sputtering cluster source. This source is based on the design of Haberland et al. (1) with the innovative introduction of a cylindrical sputtering geometry that intends to increase the particle generation efficiency also to facilitate the production of alloy clusters. A usual clusters source is constituted essentially of an atom source and aggregation chamber, to generate the particles; electrostatic lenses, to guide them; and a mass analyzer, which may, or not, select the particles by mass. For the atom source we have designed two sputtering-like sources, a home-made 1" typical planar magnetron and also a home-made cylindrical one, for axial erosion of wire targets. The aggregation chamber has a variable length ( 0-300 mm), so we can control the average size of the clusters. A skimmer, three Einzel lenses and a Bessel-Box are used to guide charged cluster through the instrument. As mass analyzer we have built Time-Of-Flight mass spectrometer. It is important to say that we choose to build almost all the components at Unicamp, these components will be described in the body of this thesis. The equipment, which is operational, showed itself capable to produce particles with more than 500 atoms, exceeding our initial expectations. We also report on magnetic characterization of clusterassembled nanostructures with cobalt clusters with 2.3 nm diameter embedded in copper matrices at different concentrations. Results from the triple fit and transport measurements were compared and showed that only at low concentration (0.5 at % Co) all experiments are consistent with the non-interacting particles assumption and the common theoretical description is appropriate. Increasing the concentration to 2.5 at.% and 5 at.% implies deviations between magnetometry and magnetotransport
Doutorado
Física
Doutor em Ciências
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Vergnaud, Céline. "Optimisation de la croissance de MoSe2 - WSe2 par épitaxie de Van der Waals pour la valleytronique." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALY038.

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Cette thèse a pour objet l’optimisation de la croissance par épitaxie par jets moléculaires dans le régime de van der Waals de couches semi-conductrices bidimensionnelles (2D) de diséléniures de métaux de transition (MoSe2, WSe2) pour les études magnéto-optiques et électriques. Cette optimisation passe par l’amélioration de la qualité cristallographique des couches sur de grandes surfaces en ajustant les paramètres de croissances (température et flux). En particulier, la maîtrise de l’état de surface du substrat est déterminante sur les mécanismes de croissance de ces couches. L’élaboration de ces matériaux de basse dimensionnalité a nécessité l’utilisation de techniques de caractérisation avancées (Diffraction de rayons X en incidence rasante, Microscopie électronique en transmission en mode haute résolution, ect). Dans cette thèse, nous nous sommes concentrés sur deux substrats particuliers : l’oxyde de silicium et le mica. Ils présentent tous les deux la particularité d’être isolants et inertes d’un point de vue électronique, ce qui est indispensable pour sonder les propriétés optiques et électriques intrinsèques des couches 2D. Finalement, nous avons développé les dopages électrique (dopage p) pour la microélectronique et magnétique (dopage Mn) pour la valleytronique
The purpose of this thesis is to optimize growth by molecular beam epitaxy in the van der Waals regime of two-dimensional (2D) semiconductor layers of transition metal diselenides (MoSe2, WSe2) for magneto-optical and electric studies. This optimization involves improving the crystallographic quality of the layers over large areas by adjusting the growth parameters (temperature and flux). In particular, the control of the surface state of the substrate is decisive on the growth mechanisms of these layers. The development of these low-dimensional materials required the use of advanced characterization techniques (Grazing incidence X-ray diffraction, High Resolved Transmission Electronic Microscopy, ect). In this thesis, we focused on two specific substrates : silicon oxide and mica. They both have the particularity of being insulating and inert from an electronic point of view, which is essential to probe the optical and electrical intrinsic properties of 2D layers. Finally, we developed electrical doping (p doping) for microelectronics and magnetic (Mn doping) for valleytronics
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Books on the topic "Nano-magnetism"

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Stefanita, Carmen-Gabriela. From bulk to nano: The many sides of magnetism. Berlin [u.a.]: Springer, 2010.

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The Open The Open Courses Library. Magnetism: Physical Methods in Chemistry and Nano Science. Independently Published, 2019.

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From Bulk To Nano The Many Sides Of Magnetism. Springer, 2008.

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Lecture Manuscripts of the 36th Spring School of the Institute of Solid State Research: Magnetism goes Nano ; Electron Correlations, Spin Transport, Molecular Magnetism. Jülich: Forschungszentrum Jülich, 2005.

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Book chapters on the topic "Nano-magnetism"

1

Barbara, Bernard. "Magnetization Reversal of Nano-particles." In Magnetism and Synchrotron Radiation, 157–208. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/3-540-44954-x_7.

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Jongh, L. J., D. A. Leeuwen, J. M. Ruitenbeek, and J. Sinzig. "Magnetic Properties of Metal Cluster Compounds. Model Systems for Nano-Sized Metal Particles." In Magnetism: A Supramolecular Function, 615–43. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-015-8707-5_30.

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Enoki, Toshiaki, Bhagvatula L. V. Prasad, Yoshiyuki Shibayama, Kazuyuki Takai, and Hirohiko Sato. "Magnetism of Nano-graphite." In Carbon Alloys, 385–94. Elsevier, 2003. http://dx.doi.org/10.1016/b978-008044163-4/50023-1.

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"Nano/micro-structured magnetism." In Nanomagnetic Materials, 1–55. Elsevier, 2021. http://dx.doi.org/10.1016/b978-0-12-822349-9.00007-9.

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"Basics of Nano-Thin Film Magnetism." In Handbook of Spin Transport and Magnetism, 38–63. Chapman and Hall/CRC, 2016. http://dx.doi.org/10.1201/b11086-6.

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Ferbinteanu, Marilena, Harry Ramanantoanina, and Fanica Cimpoesu. "Case Studies in the Challenge of Properties Design at Nanoscale." In Sustainable Nanosystems Development, Properties, and Applications, 148–84. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-0492-4.ch005.

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In the quest for nano-sized materials with potential applications in new technologies and devices, the molecular magnetism based on coordination systems shows a valuable path, including the idea of structure-property rationales. Polynuclear coordination compounds are already in the range of nanometers and many consecrated magnetic materials that can be prepared at nano-scale granulation, such as oxides, have as bonding and exchange coupling mechanisms the same causal engines identified in coordination systems. Based on this paradigm, several case studies are taken, relating the magnetic properties with methods of electron structure calculations and phenomenological models.
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Diez, L. Herrera, and D. Ravelosona. "Controlling magnetism by interface engineering." In Magnetic Nano- and Microwires, 361–79. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-08-102832-2.00012-8.

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Proenca, Mariana P., Célia T. Sousa, João Ventura, and João P. Araújo. "Cylindrical magnetic nanotubes: Synthesis, magnetism and applications." In Magnetic Nano- and Microwires, 135–84. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-08-102832-2.00006-2.

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Proenca, M. P., C. T. Sousa, J. Ventura, and J. P. Araújo. "Electrochemical synthesis and magnetism of magnetic nanotubes." In Magnetic Nano- and Microwires, 727–81. Elsevier, 2015. http://dx.doi.org/10.1016/b978-0-08-100164-6.00024-2.

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Conference papers on the topic "Nano-magnetism"

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Vavassori, Paolo. "Applications of nano-magnetism to biosensing (Conference Presentation)." In Frontiers in Biological Detection: From Nanosensors to Systems X, edited by Benjamin L. Miller, Sharon M. Weiss, and Amos Danielli. SPIE, 2018. http://dx.doi.org/10.1117/12.2293069.

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Deng, L., Yvonne Y. Li, Feng Zhou, Eric Zhu, and E. W. Hagley. "Sub-nano-Tesla, Shield-less, Field Compensation-Free Optical Wave Mixing Magnetometry for Bio-magnetism." In Frontiers in Optics. Washington, D.C.: OSA, 2017. http://dx.doi.org/10.1364/fio.2017.fw2e.1.

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Deng, L., Yvonne Y. Li, Feng Zhou, Eric Zhu, and E. W. Hagley. "Sub-nano-Tesla, Shield-less, Field Compensation-Free Inelastic Wave Mixing Magnetometry for Bio-magnetism." In Conference on Lasers and Electro-Optics/Pacific Rim. Washington, D.C.: OSA, 2018. http://dx.doi.org/10.1364/cleopr.2018.th3l.5.

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Deng, L., Yvonne Y. Li, Feng Zhou, Eric Zhu, and E. W. Hagley. "Sub-nano-Tesla, Shield-less, Field Compensation-Free Inelastic Wave Mixing Magnetometry for Bio-magnetism." In Optical Sensors. Washington, D.C.: OSA, 2018. http://dx.doi.org/10.1364/sensors.2018.sem3e.2.

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Deng, L., Yvonne Y. Li, Feng Zhou, Eric Zhu, and E. W. Hagley. "Sub-nano-Tesla, Shield-less, Field Compensation-Free Inelastic Wave Mixing Magnetometry for Bio-magnetism." In CLEO: Applications and Technology. Washington, D.C.: OSA, 2018. http://dx.doi.org/10.1364/cleo_at.2018.atu3j.7.

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ANDRIOTIS, ANTONIS N., and MADHU MENON. "THE MAGNETISM OF THE POLYMERIZED C60 MATERIALS." In Clusters and Nano-Assemblies - Physical and Biological Systems. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701879_0024.

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Zhang, Chuang, Wenxue Wang, Ning Xi, Yuechao Wang, and Lianqing Liu. "A bio-syncretic micro-swimmer assisted by magnetism." In 2015 International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO). IEEE, 2015. http://dx.doi.org/10.1109/3m-nano.2015.7425496.

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Tang, Jianwei, and Sailing He. "Ultraviolet optical magnetism from a new plasmonic resonance mode." In THE FIFTH INTERNATIONAL WORKSHOP ON THEORETICAL AND COMPUTATIONAL NANO-PHOTONICS: TaCoNa-Photonics 2012. AIP, 2012. http://dx.doi.org/10.1063/1.4750132.

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