Dissertations / Theses on the topic 'Magnet effects'
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Wu, Lijian. "Analytical modelling of electromagnetic performance and parasitic effects of permanent magnet machines." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.647997.
Full textShepherd, Marie Norfleet. "The Effects of a Middle School Magnet Program on Eighth Grade Student Performance." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30498.
Full textEd. D.
Bourgeois, Jacob. "Modeling effects of adding a flux channel to a planar magnet-coil actuator." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32875.
Full textIncludes bibliographical references (p. 38).
Planar magnet-coil actuators are used in many different MEMS devices. This report describes one way to improve the actuator range per current input of planar coil actuators. This is accomplished by adding a flux channel around and beneath the actuator's magnet. The Lorentz force is created by putting a current carrying planar coil over a magnet in an actuator assembly. The Lorentz force depends on the current vector and the magnetic field vector. In this thesis the Lorentz force is altered by changing the direction and concentration of the magnetic field. Magnetic fields may be modeled as flux lines traveling from the north face of the magnet to the south face along the least resistant path. Iron is a magnetic material with 4000 times the magnetic permeability of air, so when iron is placed in a magnetic field, the majority of the magnetic flux will travel from North to South through the iron. This "channel" alters the way the magnetic field would normally travel given the bare magnet. The magnetic flux that travels through the channel depends in part upon the channel geometry. The result of varying the width of this channel is modeled and tested in this work. The physical principle was examined in simulations by varying channel width and then extracting the corresponding actuator output. A relationship was fit to the simulated results.
(cont.) The actuator output augmentation was maximized at a critical width and remained steady thereafter. Beyond the critical width, the addition of the flux channel was able to produce more than 45% increase in the actuator force. Experimental results showed less than a 5% difference from the simulated results.
by Jacob Bourgeois.
S.B.
Lincoln, Derek M. "The electronic structure and field effects of an organic-based room temperature magnetic semiconductor." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1193833038.
Full textMese, Huseyin. "Field Oriented Control Of Permanent Magnet Synchronous Motors Using Three-level Neutral-point-clamped Inverter." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614407/index.pdf.
Full textMccaskey, Alexander Joseph. "Effects of Electron-Vibron Coupling in Single-Molecule Magnet Transport Junctions Using a Hybrid Density Functional Theory and Model Hamiltonian Approach." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/48026.
Full textMaster of Science
Ispas, Adriana. "Electrochemical Phase Formation of Ni and Ni-Fe Alloys in a Magnetic Field." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1194000718076-46815.
Full textGon?alves, Charlie Salvador. "Montagem e constru??o de um magnet?metro a efeito Kerr magneto-?ptico." Universidade Federal do Rio Grande do Norte, 2006. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16624.
Full textConselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
n this master s dissertation a Kerr Magneto Optic s magnetometer effect was set up to do characterization of samples type films fine and ultra thin, these samples will be grown after the implementation of the sputtering technique at the magnetism laboratory of of this department. In this work a cooled electromagnet was also built the water and that it reaches close values to 10kOe with a gap of 22 mm including an area of uniform field of 25mm of diameter. The first chapter treats of the construction of this electromagnet from its dimensioning to the operation tests that involve measures of reached maximum field and temperature of the reels when operated during one hour. The second chapter is dedicated to the revision of the magnetism and the magnetization processes as well as it presents a theoretical base regarding the magnetic energies found in films and magnetic multilayer. In the sequence, the third chapter, is especially dedicated the description of the effects magneto opticians the effect kerr in the longitudinal, traverse and polar configurations, using for so much only the classic approach of the electromagnetism and the coefficients of Fresnel. Distinguished the two areas of observation of the effect regarding thickness of the film. The constructive aspects of the experimental apparatus as well as the details of its operation are explained at the room surrender, also presenting the preliminary results of the measures made in one serializes of permalloy films and concluding with the results of the characterization of the first films of iron and permalloy grown here at the theoretical and experimental physics department at UFRN
Nesta disserta??o de mestrado foi montado um magnet?metro de efeito Kerr Magneto-?ptico para fazer caracteriza??o de amostras tipo filme fino e ultrafino, amostras estas que ser?o crescidas ap?s a implementa??o da t?cnica de Sputtering no laborat?rio de magnetismo deste departamento. Neste trabalho tamb?m foi constru?do um eletro?m? arrefecido a ?gua e que atinge valores pr?ximos a 10 kOe com um gap de 22 mm abrangendo uma regi?o de campo uniforme de 25 mm de di?metro. O primeiro cap?tulo trata da constru??o deste eletro?m? desde o seu dimensionamento at? os testes de opera??o que envolvem medidas de campo m?ximo alcan?ado e temperatura das bobinas quando operando durante 1 hora. O capitulo 2 ? dedicado a uma revis?o do magnetismo e dos processos de magnetiza??o bem como apresenta uma base te?rica a respeito das energias magn?ticas encontradas em filmes e multicamadas magn?ticas. Na seq??ncia, o terceiro cap?tulo, ? dedicado a descri??o dos efeitos magneto ?pticos em especial o efeito kerr nas configura??es longitudinal, transversal e polar, utilizando para tanto somente a abordagem cl?ssica do eletromagnetismo e os coeficientes de Fresnel. Distinguindo em seguida, as duas regi?es de observa??o do efeito referentes a espessura do filme. Os aspectos construtivos do aparato experimental bem como os detalhes de sua opera??o s?o explanados no quarto capitulo, apresentando tamb?m os resultados preliminares das medidas efetuadas em uma serie de filmes de Permalloy e finalizando com os resultados da caracteriza??o dos primeiros filmes de ferro e Permalloy crescidos aqui no departamento de f?sica te?rica e experimental da UFRN
Kinyo, Anthony Steven. "EFFECTS OF DISTANCE FROM INVASIVE LYTHRUM SALICARIA ON POLLINATOR VISITATION RATE AND REPRODUCTIVE SUCCESS IN NATIVE LYTHRUM ALATUM." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1127925607.
Full textNandiguim, Lamaï. "Etude du comportement magnétique et spectral de l'effet Faraday dans des oxydes métalliques dopés par des nanoparticules magnétiques de ferrite de cobalt." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES015/document.
Full textThis work is dedicated to the study of the magneto-optical properties of cobalt ferrite (CoFe2O4) nanoparticles (NP) dispersed in liquid as ferrofluid, or blocked in a solid silica matrix realized with a sol-gel method. This last dispersion is a magneto-optical composite material, obtained with a low temperature process which insures its compatibility with photonic integration technologies, to produce, in the future, integrated non-reciprocal devices. The aim of the study is, on one hand, to identify which kind of NP can improve the Faraday effect and the merit factor (ratio between the Faraday effect and the absorption) of the composite material. On the other hand, the aim is to give a better understanding of the link between the magneto-optical properties and the physical characteristics of the NP. The study has been led on NP synthetized and dispersed as ferrofluid in PHENIX laboratory (UMR CNRS 8234). Optical and magneto-optical measurements were made in Hubert Curien laboratory (UMR CNRS 5516) and completed by XMCD analysis in Synchroton SOLEIL. Results show that it is necessary to use a small size of NP (5 nm) to maximize the merit factor at a wavelength of 1,5 µm. The spectral analysis of the Faraday effect shows the influence of the cationic distribution of Co2+ et Fe3+ in the spinelle structure. Coupled to XMCD results, this analysis shows that it is necessary to maximize the quantity of Co2+ in tetraedric sites to maximize the Faraday effect at 1,5 µm and to obtain an uniaxial anisotropy which allows to orientate the NP during the gelification of the sol-gel matrix
Shalygina, E. E., A. N. Shalygin, A. M. Kharlamova, A. A. Rojnovskaya, V. V. Molokanov, N. V. Umnova, and P. P. Umnov. "Structural and Magnetic Properties of “Thick” Microwires Produced by the Ulitovsky-Taylor Method." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35314.
Full textNovikova, Irina Borisovna. "Nonlinear magneto-optic effects in optically dense Rb vapor." Texas A&M University, 2004. http://hdl.handle.net/1969.1/364.
Full textPhelps, Gretchen. "MAGNETO-OPTICAL EFFECTS AND PRECISION MEASUREMENT PHYSICS: ACCESSING THE MAGNETIC FARADAY EFFECT OF POLARIZED 3HE WITH A TRIPLE MODULATION TECHNIQUE." UKnowledge, 2014. http://uknowledge.uky.edu/physastron_etds/15.
Full textMadon, Benjamin. "Etude des effets magneto-transverses dans les matériaux ferromagnétiques : effets Righi-Leduc planaire et anomal et géométrie Corbino." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX029/document.
Full textAbstract: During this PhD we studied different electric, thermal and thermoelectric properties. For instance, we characterized the anomalous and planar Righi-Leduc effects which are the thermal equivalent of the anomalous and planar Hall effects. These effect have to be taken into account when interpreting spin Seebeck measurements.We used the technics that we developped during this study to look at the Nernst effect in InSb. We developped, a carrier mobility distribution model to explain its non-linearity at fields around 1T.We built a ferromagnetic resonance experiment in order to study the impact of thermal and thermoelectric properties in spin pumping effect.Lastly, we studied electric transport in the Corbino geometry. Corbino geometry is the one of a disc where there are no free boundaries where electric charges can accumulate. This causes the apparition of an orthoradial Hall current which consequence is the increase of resistance of the disc. We showed an increase of resistance in the Corbino geometry in CoGd and CoTb originating from anomalous Hall effect. Despite the anomalous Hall effect does not dissipate, it produces an orthoradial current which dissipates. We also found in permalloy that this increase of resistance is counterbalanced by a decrease of resistance due to the anisotropic magnetoresistance.The similarity between anomalous Hall effect and spin Hall effect which share a common microscopic origin implies that we expect in platinum the apparition of an orthoradial spin current without possibility for the charges to accumulateition. This current should dissipate just the way it does for the anomalous Hall effect.The study of this spin current will be the topic of a futur study
Subedi, Pradeep. "Collective effects in Single Molecule Magnets." Thesis, New York University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3602734.
Full textSingle molecule magnets (SMMs), such as Mn12-acetate, are composed of transition metal ions and consists of identical molecules with large ground-state spin (S = 10) and a strong uniaxial anisotropy (65 K). Below about 3 K, Mn12-acetate exhibits magnetic hysteresis with steps at specific values of longitudinal magnetic field due to resonant quantum tunneling between spin up and down projections along the easy axis. The intermolecular exchange interactions between spins on molecules are quite small and spins are considered to be independent and non-interacting.
However, the molecules do interact with each other both through magnetic dipolar interactions and through the lattice (e.g. phonons). I have investigated collective effects in SMMs due to these intermolecular interactions. In the thesis I will present experiments that explored magnetic ordering due to magnetic dipole interactions in Mn12-acetate and Mn12-acetate-MeOH. I will also present exper- iments on the onset of magnetic de agration in Mn12-acetate due to a thermal instability.
The magnetic ordering studies involved investigating the effect of transverse fields on the susceptibility of single crystals of Mn12-acetate and Mn12-acetate- MeOH. Transverse fields increase quantum spin uctuations that suppress long- range order. However, the suppression of the Curie temperature by transverse fields in Mn12-acetate is far more rapid than predicted by the Transverse-Field Ising Ferromagnetic Model (TFIFM) and instead agrees with the predictions of the Random-Field Ising Ferromagnet Model. It appears that solvent disorder in Mn12-acetate gives rise to a distribution of random-fields that further suppress long-range order. Subsequent studies on Mn12-acetate-MeOH, with the same spin and similar lattice constants but without solvent disorder as Mn12-acetate, agrees with the TFIFM.
The magnetic de agration studies involved studying the instability that leads to the ignition of magnetic deflagration in a thermally driven Mn 12-acetate crystal. When spins prepared in a metastable state reverse, Zeeman energy is released that diffuses away. In some circumstances, the heat released cannot be compensated by thermal diffusion, resulting in an instability that gives rise to a front of rapidly reversing spins traveling through the crystal. We observed a sharp crossover from relaxation driven by heat diffusion to a self-sustained reversal front that propagates at a constant subsonic speed.
Ohm, Thorsten. "Effet tunnel quantique de l'aimantation dans un aimant moleculaire, Fe8." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10187.
Full textKuszewski, Piotr. "Optical detection of magneto-acoustic dynamics." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS353.
Full textIn the developing field of spin wave-based information technology, this work investigates the possibility to use surface acoustic waves (SAW) to excite spin-waves in ferromagnetic thin layers relying on the magnetoelastic coupling. This would provide a non-inductive, efficient, and remote addressing of spin waves. In the first project we develop an experimental setup to generate electrically excited SAWs phase-locked to probe laser pulses. The magnetization dynamics is detected by an optical bridge using magneto-optical effects (Kerr and Voigt). We investigate the resonant magneto-elastic coupling in a thin film of the ferromagnetic semiconductor (Ga,Mn)As. To reach resonant coupling, the spin-wave frequency is scanned across the SAW frequency using a magnetic field. We disentangle the photoelastic contribution from the magneto-optical one, from which we obtain the amplitude of magnetization precession. We show that it is driven solely by the acoustic wave. Its field dependence is shown to agree well with theoretical calculations. Its amplitude resonates at the same field as the resonant attenuation of the acoustic wave, clearly evidencing the magnetoacoustic resonance with high sensitivity. The influence of temperature, SAW frequency and power on the coupling efficiency are studied. In the second project we use SAWs thermoelastically excited by a tightly focused laser beam on ferromagnetic metals (Ni, FeGa, Co) on a transparent substrate (glass, sapphire). Spatio-temporal maps of the surface displacement and magneto-optical signal are obtained. A high-frequency shift of the frequency spectrum of the latter gives a hint for spin-wave excitation by SAWs
Tibaldi, Pier Silvio TIbaldi. "Flexible Time-Resolved Magneto-Optical Measurements." Thesis, Uppsala universitet, Materialfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304296.
Full textVi presenterar ett tidsupplöst Kerr-mikroskop, kapabel till att mäta magnetiseringsdynamiken hos magnetiska prov tillverkade på transparenta, dubbelsdigt polerade substrat. Magnetiseringen exiteras med en strömpuls via en koplanär vågguide placerad under provet. Kerr-rotationen detekteras med hjälp av en stroboskopisk ”pump-probe” teknik som använder en ”probing” laser synchroniserad med strömpulsen. Vi rapporterar prestandatest av det tidsupplösta kerr-instrumentet för magnetiseringsdynamiken i tunna permalloy - och FePd - filmer. De experimentella resultaten för de ferromagnetiska resonans-peakarna har jämförts med beräknade värden från Kittel.
Watarai, H. "Magneto-Optical Characterization of Binding Ability of Magnetic Nanoparticles in Solution." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42805.
Full textHayne, Manus. "Magneto-optical and magneto-transport studies of the gas, liquid and solid phases of two-dimensional electrons." Thesis, University of Exeter, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357897.
Full textPoulter, Andrew James Langdale. "Magneto-optical studies of InAs/GaSb heterostructures." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299507.
Full textArdavan, Arzhang. "Millimetre-wave magneto-optics of correlated systems." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297940.
Full textKrings, Andreas. "Iron Losses in Electrical Machines - Influence of Material Properties, Manufacturing Processes, and Inverter Operation." Doctoral thesis, KTH, Elektrisk energiomvandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145243.
Full textQC 20140516
Boff, Ben Hur Bandeira. "Influência do efeito de extremidade de atuadores eletromagnéticos lineares nas indutâncias." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/179537.
Full textThis work demonstrates that the end effect in linear electromagnetic actuators can have a significant influence on the self-, mutual and synchronous inductances, with positiondependent values that can be used to measure the axial position of the armature. The study is applied to a linear synchronous electromagnetic actuator with two arrangements of quasi- Halbach permanent magnets and moving coil, which was designed for use in active and semiactive electromagnetic suspension systems. Based on the literature review presented, the end effect of permanent magnet synchronous linear machines was classified with regard to: types, causes, consequences and mitigation techniques (if necessary). In addition, the types of sensorless control methods are exemplified in order to identify a possible method to be applied to the actuator under study. It was found in the literature that sensorless control was applied to machines that have inductances with similar behavior. In terms of analysis, the distribution of the magnetic flux in the actuator is studied and a semi-analytical model was developed to calculate the value of the inductances based on the data of magnetic flux obtained through numerical simulation. Thus, the complete parametrized numerical models of the actuator were built for transient and magnetostatic simulation, and from these the inductances were obtained. The inductances are also measured experimentally, and in the analysis of the results the measurement uncertainties are calculated and a design of experiments is presented. The results of the semi-analytical and numerical models show good agreement with the experimental results. Finally, the suitability of the actuator for future application of sensorless control is discussed based on the variation of inductances due to the end effect.
Kang, Kyongha. "Crystalline structure, and magnetic and magneto-optical properties of MnSbBi thin films." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365438.
Full textDanielsson, Oskar. "Wave Energy Conversion : Linear Synchronous Permanent Magnet Generator." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7194.
Full textGhirlanda, Simone L. "Prototype and Testing of a MEMS Microcooler Based on Magnetocaloric Effect." Scholar Commons, 2006. http://scholarcommons.usf.edu/etd/3890.
Full textChan, Hung-chiu Kingsley. "Cast keepers for dental magnets : effects of laboratory procedures /." View the Table of Contents & Abstract, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31490335.
Full text陳鴻釗 and Hung-chiu Kingsley Chan. "Cast keepers for dental magnets: effects of laboratory procedures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45007706.
Full textGotsis, Harry John. "A first-principles theory of magneto-X-ray effects." Thesis, Keele University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240005.
Full textYe, Quan-Lin, Hirofumi Yoshikawa, Shunji Bandow, and Kunio Awaga. "Green magnetite (Fe3O4): Unusual optical Mie scattering and magnetic isotropy of submicron-size hollow spheres." American Institite of Physics, 2009. http://hdl.handle.net/2237/12624.
Full textCiuciulkaite, Agne. "Investigation of articial spin ice structures employingmagneto-optical Kerr effect for susceptibility measurements." Thesis, Uppsala universitet, Materialfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-265171.
Full textBharrathSingh, Kathy. "Prototypes and the perceptual magnet effect in the perception of vowels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ57602.pdf.
Full textBharrathisingh, Kathy 1966 Carleton University Dissertation Psychology. "Prototypes and the perceptual magnet effect in the perception of vowels." Ottawa.:, 2000.
Find full textVarghese, Bobin. "Resonant enhancement of magneto-optical effects using 1-D planar micro-structuration." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSES057/document.
Full textMagneto-optical (MO) devices are the basic elements of optical isolators essential for lasers an1 LIDAR, and are also employed for aircraft imaging, data storage or sensing. A periodic structuration of the core magnetic material is a way to enhance its MO behavior, and is thus useful to reduce the footprint of integrated devices or to improve the sensitivity of related sensors. However, the processing of efficient magnetic materials on photonic platforms is still challenging, because classical MO materials require an annealing temperature as high as 700°C. Using a sol-gel process, a silica matrix can be doped by magnetic nanoparticles (C0Fe204) to produce a MO material which possess a full compatibility with photonic substrates. In this work, this composite material was incorporated into an already structured template through a single step deposition at low temperature. The template was a 1-D SiJN4 grating on glass. Numerical simulations, based on RCW A methods, have been carried out to identify the suitable values of the grating period and the line-space ratio which produce a guided-mode resonance at 1.55 µm simultaneously for TE and TM polarizations, at normal incidence. MO simulations demonstrated that an enhancement of magneto-optical effects is obtained in transmission or reflection for every orientation of the applied magnetic field (Kerr or Faraday effects). The theoretical figure of merit for these structures were comparable or higher than those reported in literature which use classical MO materials. These enhancements were confirmed by experimental realizations and measurements. For instance, a Faraday rotation enhancement of 3.5 times was demonstrated compared to the reference thin-film. The c01Tesponding figure of merit was comparable or higher than those reported in literature proving the high efficiency of our structure. The results of this work are the 1st demonstration of an enhancement of every MO effect with a single device
Borge, Amruta. "GIANT MAGNETO-IMPEDANCE EFFECT IN THIN FILM LAYERED STRUCTURES." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3166.
Full textM.S.E.E.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering
Barhoumi, Rabei. "Positioning and addressing single molecule magnets with an STM tip." Thesis, Strasbourg, 2019. https://publication-theses.unistra.fr/restreint/theses_doctorat/2019/BARHOUMI_Rabei_2019_ED182.pdf.
Full textWith their large magnetic anisotropy associated with long relaxation times of the magnetization, TbPc2 molecular magnets are good candidates for encoding and recording data. Their robustness and their propensity to arrange into networks lend themselves well to a study of their electronic and magnetic structure by STM/STS at very low temperature (4.5 K). In this thesis work, it was possible to highlight a Kondo screening of the π and 4f electrons of the TbPc2 molecule by the electrons of the metal substrate. The magnetic properties of the molecule depend on their degree of interaction with the substrate and lateral interactions with other molecules. Thus, the π radical of the molecule is preserved on Au (111) but disappears on Ag (111) under the effect of a charge transfer between the substrate and the molecular monolayer. Finally, when the molecule is in strong interaction with the Cu(111) substrate, a direct access to the 4f states of the central Tb ion by STM is possible as shown by the detection of a Kondo effect on the central Tb ion
Dehbaoui, Mourad. "Analyses structurales et contrôle de l'aimantation par sonde de Hall planaire dans des dispositifs nanostructurés." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20128/document.
Full textIn an effort to combine the benefits of magnetic and electronic properties, diluted magnetic semiconductors are projected to be the basis for devices combining in their operation, both the charge and spin of electrons. Using Hall Effect magnetometer, a characterization of these materials is done by determining the magnetic orientation at low temperatures. We were also interested in molecular materials spin crossover. The magnetic sensor technology provides a path to the extension of detection techniques through the use of rapid and sensitive systems. The detection of the spin crossover nanoparticles is achieved by a planar Hall Effect sensor, made from magnetic multilayers. The work is a pioneer in the field of nano magnetic detection; it opens up new perspectives in basic research and the technological development of magnetic sensors. Improvements of the device have been completed and others are under development in order to improve sensitivity and reduce noise. The optimization should provide a novel system for detecting spin transition nanoparticles at room temperature
Wijngaard, Jan Hendrik. "Magnetic and magneto-optical properties of some transition metal compounds." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1990. http://irs.ub.rug.nl/ppn/297971859.
Full textXu, Yong. "Étude des effets de la lumière sur les propriétés électriques d’une jonction tunnel magnétique." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0256/document.
Full textThis thesis is devoted to the study of the effects of light on a magnetic tunnel junction (MTJ). A MTJ is made of a nanometer thick insulating layer sandwiched between the two magnetic layers. When an electric current is injected into such a structure, a voltage can be measured across the insulating layer. This voltage depends on the relative orientation of the magnetizations of the two magnetic layers. This is known as the tunnel magneto-resistance effect. We have shown in this thesis that voltage depending on the orientation of the magnetic layers can be measured when the junction is illuminated with light. By studying the influence of the substrate, the position of the light beam, the wave length of light and the response of the system to a laser pulse, we have been able to demonstrate the presence of photovoltaic and Seebeck effects. These results show that it is possible, thanks to the sunlight, to read the information from magnetic memory (MRAM) made of a MTJ
Meng, Xiadong. "Surface magneto-optic Kerr effect of NiCoCu multilayers." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22775.
Full textSMOKE measurements on a series of sputtered $ rm Ni sb{80}Co sb{20}15 A$/CU$(t sb{Cu}),$ where $t sb{Cu}$ is the thickness of Cu spacer layer, multilayers confirms that the coupling strength in these multilayers oscillates from antiferromagnetic (AF) coupling to ferromagnetic coupling as a function of Cu spacer layer thickness. Low-angle x-ray diffraction and SMOKE measurements on a series of AF-coupled $ rm (Ni sb{80}Co sb{20}15 A$/Cu20A) $ times$ N multilayers with bilayer numbers N ranging from 8 to 100 shows that cumulative interface roughness increases with increasing N, as do the saturation field and coercivity. This is possibly due to the out-of-plane anisotropy associated with cumulative interface roughness in multilayers.
An AF-coupled $ rm (Ni sb{70}Co sb{30}15 A$/Cu20A) $ times$ 10 was continually annealed up to 400$ sp circ$C in several steps, and the magnetic behaviour of the sample was evaluated as a function of annealing temperatures. $ rm (Ni sb{70}Co sb{30}15 A$/CU20A/Ni$ rm sb{70}Co sb{30} A$/CU20A) $ times$ 5 multilayer was used for investigating the AF coupling between magnetic layers of unequal thicknesses. Finally, an AF-coupled $ rm (Ni sb{70}Co sb{30}15 A$/Cu20A/Ni$ rm sb{70}Co sb{30}15 A$/Cu35A) $ times$ 5 multilayer was sputtered and used to study the magnetization of an AF-coupled multilayer with two different coupling strengthes.
Cristaldo, Cesar Flaubiano da Cruz. "On droplet combustion: effect of magneto relaxation heating." Instituto Nacional de Pesquisas Espaciais (INPE), 2013. http://urlib.net/sid.inpe.br/mtc-m19/2013/03.25.17.57.
Full textIn this work, the influence of an external alternating magnetic field on heating, va-porization and combustion of a ferrofluid (liquid with dispersed magnetic nanoparticles) droplet is investigated. The response of the magnetic nanoparticles to the magnetic field generates heat inside the droplet, due to magneto relaxation, which acts as a heat source. This phenomenon is produced by friction (viscous dissipation) between rotating nanoparticles and the liquid surrounding them. The rotating motion of the nanoparticles is induced by the magnetic dipole fixed on each nanoparticle, which tends to align itself with the magnetic field. In the absence of magnetic field, Brownian motion of the liquid molecules is responsible for misaligning the dipoles, after collisions with the nanoparticle surface. Under the influence of an external alternating magnetic field, the process of aligning and misaligning repeats itself in each cycle, producing heat by viscous dissipation, due to a periodically reversing nanoparticle circular motion. In the present analysis the process of magneto relaxation heating, together with heat transfer from the ambient is studied. These two mechanisms (magnetic heating and heat flux fro the gas-phase) contribute to droplet heating, hence increasing the vaporization rate of ferrofluid droplets. Assuming a very large magnetic power and a uniform distribution of nanoparticles, the droplet core is uniformly heated. A thermal boundary layer is established in the liquid-phase adjacent to the droplet surface due to heat flux from the ambient atmosphere. The temperature profile inside the thermal boundary layer is obtained in appropriate time and length scales. In the present model, the ferrofluid droplet is heated up to its boiling temperature in a very short time. Additionally, under certain conditions the temperature inside the thermal boundary layer can become higher than the temperature at the droplet surface. This leads to boiling occurs inside the droplet rather than at the surface, as in classical models. The temperature difference between the thermal boundary layer and the droplet surface results in an extra heat flux to the droplet surface, which increases the vaporization rate. Moreover, the results point out that the thermal boundary layer depends directly on the oxidant Lewis number but the vaporization rate reciprocally on it.
Chang, Chia-Ming. "Coupling effect of finite magneto-electric laminate composites." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1472130571&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
Full textGonzalez, Gabriel. "Electron transport in single molecule magnet transistors and optical [lambda] transitions in the ¹⁵N-V⁻ center in diamond." Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002740.
Full textKahl, Sören. "Bismuth iron garnet films for magneto-optical photonic crystals." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3711.
Full textThe thesis explores preparation and properties of bismuthiron garnet (BIG) films and the incorporation of BIG films intoone-dimensional magneto-optical photonic crystals (MOPCs).
Films were prepared by pulsed laser deposition. Weinvestigated or measured crystallinity, morphology,film-substrate interface, cracks, roughness, composition,magnetic coercivity, refractive index and extinctioncoefficient, and magneto-optical Faraday rotation (FR) andellipticity. The investigations were partly performed onselected samples, and partly on two series of films ondifferent substrates and of different thicknesses. BIG filmswere successfully tested for the application of magneto-opticalvisualization. The effect of annealing in oxygen atmosphere wasalso investigated - very careful annealing can increase FR byup to 20%. A smaller number of the above mentionedinvestigations were carried out on yttrium iron garnet (YIG)films as well.
Periodical BIG-YIG multilayers with up to 25 single layerswere designed and prepared with the purpose to enhance FR at aselected wavelength. A central BIG layer was introduced asdefect layer into the MOPC structure and generated resonancesin optical transmittance and FR at a chosen design wavelength.In a 17- layer structure, at the wavelength of 748 nm, FR wasincreased from -2.6 deg/µm to -6.3 deg/µmat a smallreduction in transmittance from 69% to 58% as compared to asingle-layer BIG film of equivalent thickness. In contrast tothick BIG films, the MOPCs did not crack. We were first toreport preparation of all-garnet MOPCs and second toexperimentally demonstrate the MOPC principle inmagneto-optical garnets.
Prescimone, Alessandro. "Effect of high-pressure on molecular magnetism." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4619.
Full textLui, Emily. "Multi-Physics Interactions for Coupled Thermo-Electro-Magneto-Mechanical Effects." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306897291.
Full textSamin, Adib J. Jr. "An analysis of neutron radiation effects on NdFeB permanent magnets." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405899609.
Full textNguyen, Thi Ngoc. "Caractérisation et modélisation d'un micro-capteur magnétoélectrique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS203/document.
Full textMagneto-electric (ME) sensors have been demonstrated as a promising alternative for the detection of weak magnetic signals with high sensitivity. To date, most applications focused on the use of bulk piezoelectric materials on which magnetostrictive thin films are deposited leading to millimeter-sized devices. The integration of such devices into micro-electro-mechanical systems (MEMS), bringing smaller size and lower power consumption, involves addressing several scientific issues ranging from the integration of active materials on silicon to the strong reduction in amplitude of generated signals related to the size reduction of the sensor.In this context, the first goal of this thesis work was to integrate high crystalline quality piezoelectric thin films on silicon.Pb(Zr ₓTi ₁ ₋₁)O₃ (PZT) with a morphotropic composition (x=0.52) having high electromechanical coupling factor was chosen. Silicon is a necessary template as it allows for the use of conventional clean room processes for the realization of the microsystem. The crystalline quality of the active films is directly linked to the buffer layers that promote the crystalline growth on silicon. For this purpose, Yttria-stabilized Zirconia (YSZ) was used in combination with CeO₂ and SrTiO₃ to allow further growth of epitaxial perovskites. The choice of the bottom electrode material (SrRuO₃ or La ₀ ,₆₆Sr₀₃₃MnO₃ in this work) further tunes the crystalline orientation of the PZT layer.To probe the potential of such PZT thin films for ME devices, the first step was to characterize the electromechanical properties of this material in a free standing cantilever structure. Under an applied electric field, the measured displacement of the epitaxial PZT-based cantilevers is characterized by a coefficient d₃₁ =-53pmV⁻¹ , a reduced value with respect to the bulk material but that can be enhanced by further optimizing the film growth. The second step consists in ascertaining the ability of the cantilever to be used as resonator. For that purpose, first characterizations of oscillators have been performed to extract the resonant frequencies and the associated quality factors. Then, the resonant frequency shift with DC bias-induced stress was measured. Finally, a magnetostrictive layer of TbFeCo was added on the PZT cantilevers to sense magnetic field based on the ME effect. The resulting resonant frequency shift with external applied magnetic field was characterized with a typical sensitivity of 10’s of µT
Alexandrou, Marios. "Magneto-optic Kerr and Hall effect measurements for the characterisation of bit patterned media." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/magnetooptic-kerr-and-hall-effect-measurements-for-the-characterisation-of-bit-patterned-media(fba9cd67-86c0-4382-ad65-52c521f70e5d).html.
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