Dissertations / Theses: 'Magnetotransport'

1

Mennicke, Ralph T. "Sensing magnetotransport." Thesis, University of York, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441021.

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Rich, Thalia L. "Magnetotransport in electron waveguides." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36433.

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Nam, Moon-Sun. "Magnetotransport in BEDT-TTF salts." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342589.

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4

Snell, B. R. "Magnetotransport in short semiconductor structures." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380110.

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5

Moseley, Dominic. "Magnetotransport experiments in the ferropnictides." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24798.

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This thesis concerns the magnetotransport properties of the iron-based superconductors, and in particular, the ferropnictides. In the low doped ferropnictides, linked structural and magnetic transitions occur which significantly alter the electronic behaviour. Simultaneous to the establishment of the magnetic ordering is the creation of small Fermi surface pockets. It has been shown that some of these Fermi surface pockets have Dirac Cone characteristics. The primary work in this thesis focuses on the existence of non-saturating quasi-linear magnetoresistance in the underdoped ferropnictides. This feature has been seen as the hallmark of Dirac cone physics due to the commonly applied quantum linear magnetoresistance model. We have explored this hypothesis by performing a series of magnetotransport experiments using the van der Pauw method on undoped BaFe$_{2}$As$_{2}$, low cobalt doped BaFe$_{1.985}$Co$_{0.015}$As$_{2}$ and superconducting BaFe$_{1.96}$Co$_{0.04}$As$_{2}$. Scattering centres have been systematically introduced using 3-MeV proton irradiation. The quantum linear magnetoresistance model predicts the quasi-linear magnetoresistance should vary with carrier scattering. We describe these experiments, and draw the conclusion that the quantum linear magnetoresistance model is incorrectly applied. Other models to explain the quasi-linear magnetoresistance are reviewed. Speculation as to the cause of magnetic hysteresis in the magnetoresistance found in some of the parent crystals studied is presented. The Hall resistivity in the parent and underdoped ferropnictides shows a clear non-linear response suggesting that the single carrier model is invalid. We find that the Hall resistivity is insensitive to the introduction of disorder. Various models are reviewed including the anomalous Hall Effect and the antiferromagnetism related anisotropic quasiparticle lifetime model. Furthermore, magnetotransport scaling techniques are considered. Only the modified Kohler's rule is satisfied and this is shown to have an intriguing Co doping dependence.

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Paudel, Bhim L. "Magnetotransport in GaMnAs Based Microstructures." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1331927548.

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Hapke-Wurst, Isabella. "Resonanter Magnetotransport durch selbstorganisierte InAs-Quantenpunkte." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965263339.

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8

Boye, Shawn Alexander. "Magnetotransport Measurements of Ni Thin Films." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4653.

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This thesis presents transverse magnetoresistance (MR) and Hall resistivity measurements of nickel thin films at temperatures between 280 and 455 K and pressures up to 6 GPa. An experimental system was developed for conducting precise magnetotransport measurements using the current reversal and van der Pauw techniques in combination with a 10 T superconducting magnet. Polycrystalline Ni_0.985O_0.015 thin film samples were manufactured with preexisting point contacts allowing highly reproducible magnetotransport measurements at pressure in the diamond anvil cell (DAC).

The magnetic resistivity above the technical saturation of the magnetization was found to decrease linearly to the highest applied fields, 10 T, while the field derivative, 0.010-0.018 µΩ cm T^-1 between 280 and 316 K, increased with temperature and decreased with pressure. The decrease in the magnetoresistance is attributed to spin wave damping of electron-magnon scattering processes at high fields. The magnon mass, 535(14) meV Å² at 0 K and 0 GPa, determined from longitudinal magnetic resistivity theory is a slightly increasing function of pressure. Correlation between the zero field resistivity and the extraordinary Hall coefficient (EHC) confirmed side jump scattering as the dominant diffusion mechanism at 0 GPa, however, skew scattering was found to become increasingly important with pressure.

The effect of oxygen and pressure on the density of states (DOS) at the Fermi level was investigated through total energy band structure calculations using a periodic supercell of 64 atoms to simulate the sample chemistry. The DOS of Ni_0.985O_0.015 at the Fermi level was found to increase by 27% at 10 GPa relative to 0 GPa. However, when compared to the results for pure Ni, decreases of 60% and 23% occurred for the corresponding calculations at 0 and 10 GPa. The relative differences in the magnetic resistivity are attributed to competing effects between the DOS, average magnetic moment and magnon mass.

The technique developed for conducting magnetotransport measurements at pressure is applicable to the study of electronic diffusion in ferromagnets as well as geophysical problems such as the geodynamo.

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Walter, Theresia. "Struktur und Magnetotransport laserdeponierter Lanthanmanganat Dünnschichtsysteme." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1091095462390-98045.

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Die vorliegende Dissertation "Struktur und Magnetotransport laserdeponierter Lanthanmanganat Dünnschichtsysteme" beschäftigt sich mit der Herstellung, den strukturellen Eigenschaften und dem Magnetotransport von ferromagnetisch-metallischen Lanthanmanganat-Schichten La0.7A0.3MnO3 (A=Sr, Ca) und Schichtsystemen. Die untersuchten Schichten und Schichtsysteme wurden mittels Laserablation in "off-axis" Geometrie auf einkristallinen oxidischen Substraten abgeschieden. An einer Serie von polykristallinen La0.7Sr0.3MnO3/Y:ZrO2(100) Schichten wurde der Korngrenzen-Magnetowiderstandseffekt ferromagnetisch-metallischer Manganate untersucht. Durch Variation der Substrattemperatur während der Abscheidung läßt sich die Textur graduell einstellen. Untersuchungen des quantitativen Verhaltens des Magnetowiderstandes zeigen eine klare Korrelation des Niederfeld-Magnetowiderstandes und des Hochfeld-Magnetowiderstandes. Durch Untersuchungen an einer nichttexturierten Schicht in hohen gepulsten Magnetfeldern konnte auf einen indirekten Tunnelprozeß der Elektronen durch die Korngrenze entsprechend einem Modell von Lee et al. geschlossen werden, wobei die magnetische Ordnung der Korngrenze antiferromagnetisch ist. An den epitaktischen Schichtserien La0.7Ca0.3MnO3/NdGaO3(110) und La0.7Sr0.3MnO3/SrTiO3(100) und an heteroepitaktischen Multilagen (La0.7Sr0.3MnO3/SrTiO3)n/SrTiO3(100) wurden die strukturellen, magnetischen und elektrische Eigenschaften in Abhängigkeit von der Schichtdicke und der Einfluß der Grenzflächeneigenschaften untersucht. Allgemein zeigte sich, daß die mechanische Verspannung und Mikrostruktur der Schichten einen großen Einfluß auf deren physikalischen Eigenschaften haben. Die beobachtete Reduzierung der Curie-Temperatur, der Metall-Isolator-Übergangstemperatur und der spontanen Magnetisierung kann auf den finite-size Effekt und auf die Ausbildung von Perkolationspfaden (metallische Cluster in nichtmetallischer Matrix) in den ultradünnen Schichen zurückgeführt werden.

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10

Kim, Gil-Ho. "Magnetotransport in low dimensional semiconductor structures." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/244953.

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This dissertation describes low-temperature electronic transport measurements on semiconductor structures of restricted dimensionality. The experiments fall into two sets. The first concerns anisotropic magnetotransport measurements and electron focusing in a varying external magnetic field. These are performed using MBE-grown high mobility two-dimensional electron gases formed on (311)B GaAs substrates. The second is a study of magnetic field induced insulator-quantum Hall liquid transitions performed on GaAs-AIGaAs heterostructures in which a number of InAs monolayers are inserted in the centre of a GaAs quantum well. The sample structures were characterised by STM, TEM, STEM, and AFM. Interest in electron transport on high-index GaAs surfaces is increasing, especially since the advent of patterned substrate regrowth. An anisotropic mobility in orthogonal directions seems to be universal for electron gases grown on (311)B-oriented GaAs substrates. The anisotropy depends on the two-dimensional electron gas carrier density, but mobilities are always higher in the [233] direction. The interface roughness scattering is a possible cause of the mobility anisotropy. The electron focusing results demonstrate that the effective mass and Fermi surface are isotropic even through the mobility is anisotropic. An explanation is proposed based on interface roughness scattering. In the second part, a magnetically induced direct transition from an insulating state at zero magnetic field to quantum Hall effect states with Hall resistance Pxy = h/2e2 and Pxy = h/e2 and back to an insulating state at higher field is observed. The phase boundaries are plotted as a function of disorder and magnetic field using two methods, firstly the temperature independent Pxx points and secondly the maxima in CJxx. This experimental phase diagram is related to the disorder induced collapse of spin splitting in the lowest Landau level obtained from activation energy studies.

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11

Goddard, Paul. "Magnetotransport studies of layered metallic systems." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275491.

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12

Martin, Robert W. "Quantum magnetotransport in strained layer heterostructures." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315751.

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13

Deacon, Russell. "Magnetotransport studies of InAs/GaSb superlattices." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427872.

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14

Greene, Simon Kenneth. "Magnetotransport effects in low dimensional semiconductors." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358645.

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15

Walter, Theresia. "Struktur und Magnetotransport laserdeponierter Lanthanmanganat Dünnschichtsysteme." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24356.

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Die vorliegende Dissertation "Struktur und Magnetotransport laserdeponierter Lanthanmanganat Dünnschichtsysteme" beschäftigt sich mit der Herstellung, den strukturellen Eigenschaften und dem Magnetotransport von ferromagnetisch-metallischen Lanthanmanganat-Schichten La0.7A0.3MnO3 (A=Sr, Ca) und Schichtsystemen. Die untersuchten Schichten und Schichtsysteme wurden mittels Laserablation in "off-axis" Geometrie auf einkristallinen oxidischen Substraten abgeschieden. An einer Serie von polykristallinen La0.7Sr0.3MnO3/Y:ZrO2(100) Schichten wurde der Korngrenzen-Magnetowiderstandseffekt ferromagnetisch-metallischer Manganate untersucht. Durch Variation der Substrattemperatur während der Abscheidung läßt sich die Textur graduell einstellen. Untersuchungen des quantitativen Verhaltens des Magnetowiderstandes zeigen eine klare Korrelation des Niederfeld-Magnetowiderstandes und des Hochfeld-Magnetowiderstandes. Durch Untersuchungen an einer nichttexturierten Schicht in hohen gepulsten Magnetfeldern konnte auf einen indirekten Tunnelprozeß der Elektronen durch die Korngrenze entsprechend einem Modell von Lee et al. geschlossen werden, wobei die magnetische Ordnung der Korngrenze antiferromagnetisch ist. An den epitaktischen Schichtserien La0.7Ca0.3MnO3/NdGaO3(110) und La0.7Sr0.3MnO3/SrTiO3(100) und an heteroepitaktischen Multilagen (La0.7Sr0.3MnO3/SrTiO3)n/SrTiO3(100) wurden die strukturellen, magnetischen und elektrische Eigenschaften in Abhängigkeit von der Schichtdicke und der Einfluß der Grenzflächeneigenschaften untersucht. Allgemein zeigte sich, daß die mechanische Verspannung und Mikrostruktur der Schichten einen großen Einfluß auf deren physikalischen Eigenschaften haben. Die beobachtete Reduzierung der Curie-Temperatur, der Metall-Isolator-Übergangstemperatur und der spontanen Magnetisierung kann auf den finite-size Effekt und auf die Ausbildung von Perkolationspfaden (metallische Cluster in nichtmetallischer Matrix) in den ultradünnen Schichen zurückgeführt werden.

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16

Chandra, Nikhil. "Der Einfluss der Randstreuung auf ballistischen Magnetotransport." Diss., lmu, 2000. http://nbn-resolving.de/urn:nbn:de:bvb:19-2147.

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17

Duijn, Henricus Gerardus Maria. "Magnetotransport and magnetocaloric effects in intermetallic compounds." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/83091.

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18

Freitag, James M. (James Mac). "Structural and magnetotransport properties of nickelcobalt multilayers." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24003.

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Ferromagnetic/ferromagnetic Ni/Co multilayers with component layer thicknesses ranging from 40 A down to 5 A were prepared by DC-magnetron sputtering. Due to the fact that Ni and Co alloys share a common d band, it is expected that the total resistance of the multilayers, including the elemental resistance of the layers and the resistance of the interdiffused alloyed region at the interfaces, will be lower than for other 3d transition metal combinations. Consequently, the magnetoresistance ratio $ Delta rho/ rho$ is expected to be enhanced.
Structural characterization by grazing-angle X-ray reflectivity reveals high-quality layered structures with a well-defined composition modulation along the film growth direction. Wide-angle X-ray diffraction scans display the polycrystalline nature of the Ni/Co multilayers which grow in an FCC phase with a preferred (111) orientation and a fraction of (200) structural domains.
Measurements of the magnetotransport properties of these multilayers indicate that the magnetoresistance (MR) effect, $ Delta rho sim0.35 mu Omega cdot$cm, is roughly constant over the entire compositional range. The MR ratio $ Delta rho/ rho,$ which is as high as 3.0% in a Si/(Ni40A/Co5A) $ times$ 6 multilayer, is therefore more strongly dependent on the zero-field resistivity $ rho.$ By fitting a semi-classical model to the resistivity compositional variation, we determined the interface contribution to the resistivity. The MR measurements as well as the magnetic anisotropy of the films, studied by vibrating sample magnetometry (VSM) and magneto-optical Kerr effect (MOKE) magnetometry, are consistent with the origin of the observed MR effect being anisotropic magnetoresistance (AMR). The highest magnetic sensitivity measured at zero-field and constant in the range from ${ sim}{-}10$ Oe to +10 Oe was 0.1%/Oe. This value compares well with other alloys being developed as magnetic sensors. (Abstract shortened by UMI.)

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19

Khym, Sungwon. "Magnetotransport studies of semimetallic InAs/GaSb structures." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325145.

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20

Symons, David Malcolm. "Magnetotransport studies on new GaSb/InAs heterostructures." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260114.

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21

Creeth, Graham Leslie. "Growth and magnetotransport studies of epitaxial graphene." Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1363/.

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In this thesis single-crystal 4H silicon carbide is decomposed by annealing in ultra-high vacuum conditions, forming a surface layer consisting of a few atomic layers of graphitic carbon (graphene) arranged in known crystallographic register with the substrate material. The layers of graphene on the (0001) face form the subject of the thesis, and their surface morphology, crystallography and electronic transport properties are investigated in order to gain insight into the growth process with a view to improving the quality of the graphene (assessed in terms of lateral grain size, and coherence of electronic transport). Graphene quality is improved following changes to the annealing procedure based on understanding of growth mechanisms, and the resulting material is characterised using a range of surface-sensitive techniques as well as extensive analysis of electronic transport phenomena. Comparisons made between the graphene produced by the initial and improved processes indicate an order of magnitude increase in structural coherence as a result of the changes made, with associated improvements in electronic characteristics. Magnetotransport measurements are presented which demonstrate the two-dimensional nature of the material. These can also be used to extract values for rates associated with the various scattering mechanisms present, which in turn give insight into the electronic coherence, linking this with the physical properties. Consideration of electronelectron interaction effects is required in order to fully explain the magnetotransport behaviour seen. Detailed consideration of surface properties seen at intermediate stages in the decomposition process (including a previously unreported surface reconstruction) is used to suggest a change to established growth procedures which if successful has the potential to further improve the quality of material.

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22

Marquardt, Ronald R. McGill T. C. McGill T. C. "Quantum magnetotransport studies of semiconductor heterostructure devices /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10172007-111750.

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23

Howell, D. F. "Studies of two-dimensional electron systems in semiconductors at high magnetic fields." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253390.

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24

Mallet, Jennifer. "Transport studies of the fractional quantum hall effect." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237872.

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25

Martin, Patrick Michael. "Magnetospectroscopy of electron and hole tunnelling in (AlGa) as resonant tunnelling structures." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363614.

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26

D'Anjou, Benjamin. "Theory of anomalous magnetotransport in triple quantum dots." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110764.

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In this thesis, we study Aharonov-Bohm oscillations arising in electronic transport through a triple quantum dot in a ring arrangement in a transverse magnetic field. We start from a microscopic Hubbard Hamiltonian and the Nakajima-Zwanzig generalized master equation to show that in the large-bias regime, transport through the triple dot can be described using a coherent master equation in the Lindblad form. We solve this equation numerically and analytically to compute the current transmitted through the triple dot. We show that the current exhibits oscillations of period h/ne with n>2 when the magnetic flux threading the ring is varied, and that under certain conditions the amplitude of the n=3 period is much larger than the amplitude of the n=2 period. We include a discussion of the effect of electric-field-induced dephasing on the h/ne oscillations, and show that the inter-dot dephasing rates increase as the ring size increases, causing the anomalous dominance of the n=3 oscillations to disappear in larger rings.
Dans ce mémoire, nous étudions les oscillations de Aharonov-Bohm apparaissant dans le transport électronique à travers trois boîtes quantiques formant un anneau traversé par un champ magnétique. Nous utilisons un Hamiltonien microscopique de Hubbard et l'équation maîtresse généralisée de Nakajima-Zwanzig pour montrer que lorsqu'une grande tension électrique est appliquée, le transport peut être décrit à l'aide d'une équation maîtresse cohérente dans la forme de Lindblad. Nous résolvons cette équation numériquement et analytiquement pour calculer le courant électrique transmis à travers la triple boîte quantique. Nous montrons que le courant oscille avec une période h/ne en fonction du flux magnétique traversant l'anneau et que, sous certaines conditions, l'amplitude de la période n=3 est beaucoup plus grande que l'amplitude de la période n=2. Nous discutons également de l'effet du déphasage induit par les fluctuations du champ électrique environnant sur l'amplitude des oscillations de périodes h/ne et montrons que les taux de déphasage entre les paires de boîtes quantiques augmentent quand la taille de l'anneau augmente, causant la disparition de la domination anormale des oscillations n=3 dans les anneaux mésoscopiques de plus grande taille.

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27

Daly, Matthew Stuart. "High pressure magnetotransport studies of InAs/GaSb heterostructures." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318520.

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Dalton, Karen Sonya Helen. "Pulsed field studies of magnetotransport in semiconductor heterostructures." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325936.

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Cooper, L. J. "Magnetotransport studies of InAs/GaSb/AlSb-based structures." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597965.

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A reliable procedure has been developed which facilitates the fabrication of low-leakage front and back gated lateral transport devices in which electrons and holes reside in adjacent layers. This gating permits the alteration of the electron and hole densities in such devices almost independently of one another. A simple processing technique has also been developed for resonant inter-band and hybrid inter/intra-bond tunnelling devices. In the absence of a barrier between the layers in which the charge resides, it is shown that the wavefunctions of electrons and holes hybridise, causing an energy gap to form in the dispersion relation of the hybrid particles. This manifests itself in lateral transport measurements as a resistance peak when the Fermi energy in the system is made to lie in this "gap" by the action of the gates. The resistance resonance is seen to disappear as a function of temperature and in-plane magnetic field. The results of a simple numerical model are shown to predict the broad features in the experimental data and allow the extraction of the magnitude of the energy gap in the system. Anomalous low-field positive magnetoresistance in an in-plane magnetic field is discussed in the context of wavefunction movement in the growth plane and the antilocalisation effects of asymmetry. In a perpendicular magnetic field, Landau levels are formed in the system and the transport shows Shubnikov-de Haas oscillations and quantum Hall plateaux originating from either carrier type. So-called "compensated Hall plateaux" are observed and the absence of a completely compensated "v=0" plateau is discussed. Magnetic field induced charge transfer between the electron and hole layers which depends on the inter-layer tunnelling is observed. Tilted magnetic field measurements are performed to extract the effective g-factor of the electrons in the system and the effect of electron-hole coupling on its value is discussed.

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Meng, Tiejun. "Magnetization properties and magnetotransport of cobalt nano-structures." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611529.

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Esien, Kane. "Magnetotransport measurements of NiFe thin films and nanostructures." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/99978/.

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A custom built thermal evaporator equipped with in situ electrical transport probes and an electromagnet, designed to investigate magnetic thin films and nanostructures, was constructed and calibrated. Magnetoresistance measurements were used to characterise a 20 nm thick film grown in 2 nm steps and measured in situ as a function of film thickness. It was found that the thin film had a smaller than expected anisotropic magnetoresistance (AMR) signal of 0.024%. It was suggested that an oxide formed at each 2nm thick layers during the growth phase altered the conductivity of the film and caused the measured AMR to be anomalously small. Lateral spin valves fabricated from a range of ferromagnetic and normal metal components were investigated. NiFe/Au/NiFe lateral spin valves were the most thoroughly investigated to determine the spin diffusion length in the Au, the spin polarisation of NiFe and the injection efficiency at the NiFe/Au interface. Lateral spin valves fabricated from NiFe/Al/NiFe and utilising tunnelling contacts were also investigated and a pure spin current detected. Other devices, including a non-local lateral spin valve dual spin injection structure, were fabricated and measured. Nanomachining using diamond coated silicon nitride atomic force microscope (AFM) tips was employed to modify nickel iron (NiFe) nanowires. The modifications to nanowires in this way subsequently altered the observed domain wall motion in the wires. AFM nanomachining was found mostly to increase the coercive field of the nanowires owing to the formation of a pinning site for domain walls. Magnetoresistance measurements were used to study the effect of machining nanowires of varying widths and thickness. Theoretical predictions regarding the change in coercive field due to machining were larger than those experimentally measured. Domain wall anisotropic magnetoresistance (DW AMR) was also studied as a function of width for two thicknesses of nanowire (10nm and 20nm). Deviation from existing theoretical models was observed consistently for both wire thicknesses. A dependence of the DW AMR on the proximity to the phase boundary between different domain wall types was observed for each thickness of nanowire studied.

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Gilbertson, Adam Maurick. "Spin and magnetotransport properties of narrow gap semiconductors." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/11387.

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Raičević, Ivana. "Charge glassiness and magnetotransport in lightly doped cuprates." Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-07162009-144126.

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Thesis (Ph. D.)--Florida State University, 2009.
Advisors: Dragana Popović [and] Vladimir Dobrosavljević, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed on Nov. 2, 2009). Document formatted into pages; contains xvi, 106 pages. Includes bibliographical references.

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Huang, Nathaniel Jian. "Magnetotransport in graphene and related two-dimensional systems." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:4944f2d4-83e5-44ee-90f5-faa35acac80f.

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This thesis describes studies on two-dimensional electron gases (2DEG) in graphene and related 2D systems. Magnetotransport investigations specifically in graphene and its bilayer system are demonstrated in detail, while the experimental techniques presented in this thesis are widely applicable to a large variety of other 2D materials. Chapter 1 gives an introduction and motivation for the principal topic presented in this thesis, with a general introduction to carbon nano-materials and an overview of the current state of graphene-related research and technological development (RTD). Chapter 2 establishes a basic theoretical framework which is essential for interpreting the results presented in this thesis, starting with the crystal and electronic band structures of graphene and its bilayer, followed by high magnetic fields effects on transport properties in these 2D systems. Chapter 3 details the experimental methods directly related to the presented work. The next three chapters report experimental results of three specific magnetotransport studies. Chapter 4 reports the disorder effects on epitaxial graphene in the vicinity of the Dirac point. Quadratic increases of carrier densities with temperature are found to be due to intrinsic thermal excitation combined with electron-hole puddles induced by charged impurities. It is also shown that the minimum conductivity increases with increasing disorder strength, in good agreement with quantum-mechanical numerical calculations. Chapter 5 reports measurements of the quantum Hall effect in epitaxial graphene showing the widest quantum Hall plateau observed to date extending over 50 T, attributed to a magnetic field dependent charge transfer process from charge reservoirs with exceptionally high densities of states in close proximity to the graphene. Using a realistic framework of broadened Landau levels this process is modelled in excellent agreement with experimental results. In Chapter 6, energy relaxation of hot carriers in graphene bilayer systems is investigated from measurements on Shubnikovde Haas oscillations and weak localisation. The hot-electron energy loss rate follows the predicted T⁴ power-law at carrier temperatures from 1.4 up to about 100 K, due to electron-acoustic phonon interactions. Comparisons are made between graphene monolayer and bilayer systems and a much stronger carrier density dependence of the energy loss rate is found in the bilayer system. This thesis concludes with a summary of the most important findings of the topics that have been discussed. The significance and limitations of the present research are listed. Some suggestions and outlook are given for possible improvements and interesting areas of future research and development.

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Geishendorf, Kevin [Verfasser], Kornelius [Akademischer Betreuer] Nielsch, Kornelius [Gutachter] Nielsch, and Georg [Gutachter] Woltersdorf. "Magnetotransport Experiments in Co₃Sn₂S₂ Microstructures : Magnetotransport Experimente in Co3Sn2S2 Mikrostrukturen / Kevin Geishendorf ; Gutachter: Kornelius Nielsch, Georg Woltersdorf ; Betreuer: Kornelius Nielsch." Dresden : Technische Universität Dresden, 2020. http://d-nb.info/1227311044/34.

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36

Rüster, Christian. "Magnetotransport effects in lateral and vertical ferromagnetic semiconductor junctions." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=980715393.

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37

Weichsel, Christian. "Magnetotransport und Kapazitätsspektroskopie an zweidimensionalen Elektronengasen und InAs-Quantenpunkten." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=970608616.

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38

Maher, Matthew John. "Magnetism and magnetotransport in Fe and Co nanocluster assemblies." Thesis, University of Leicester, 2002. http://hdl.handle.net/2381/30660.

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Vibrating sample magnetometry showed that dilute assemblies of unfiltered Fe and Co nanoclusters well above their blocking temperature are superparamagnetic and the magnetisation curves follow the Langevin function with a tight size distribution around a mean of 2.2 nm. Magnetisation curves of blocked non-interacting particles showed a small coercivity and a remanence value consistent with a uniaxial anisotropy in the particles. At low temperature, the films assume an asperromagnetic state and fits to this model indicated an enhanced anisotropy constant by a factor of ten over the bulk. Cluster assembled films with packing densities up to 30 at % concentration are described by the Langevin function with an increased mean particle size. As the packing density is increased further, the behaviour deviates from the super-paramagnetic model towards a correlated spin glass. At low temperatures the anisotropy energy of the particles is greater than the exchange energy and the sample is asperromagnetic. In pure Fe cluster assembled films (~500 A) thick capped by Ag a transition, as the temperature rises from 2 to 300K, from an asperromagnetic state to a correlated spin glass occurs. Uncapped Fe cluster films displayed only correlated spin glass behaviour even at 2K. Giant magnetoresistance has been observed in the cluster assembled systems Fex-Ag1-x, FexCu1-x and CoxAg1-x and investigated for varying cluster packing densities. The results were compared to models formulated for granular alloys and were found to be in good agreement for < 16% cluster films. As the cluster interactions are increased, the peak of the GMR, at H~0, was found to be quenched due to the magnetic correlations among the particles. Co cluster films created with Ag or SiO capping layers displayed a ferromagnetic - antiferromagnetic interaction caused by partial oxidation of the clusters. Magnetometry of an uncapped Co cluster film held in UHV has shown spin glass behaviour at 2K as found for Fe cluster films.

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39

Venditti, Mario J. "Magnetotransport along non parabolically confined quasi-one-dimensional channels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ59275.pdf.

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40

Gayer, Nils [Verfasser]. "Magnetotransport und Thermoelektrik in zylindrischen GaAs-Halbleiterstrukturen / Nils Gayer." München : Verlag Dr. Hut, 2018. http://d-nb.info/1170474128/34.

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41

Melhuish, Gavin. "Magnetotransport studies of artificially disordered two-dimensional electron gases." Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425295.

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42

Alper, Muersel. "Electrodeposited magnetic superlattices : (growth, characterization, magnetic and magnetotransport properties)." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261317.

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43

PARENT, FRANCK. "Elaboration et proprietes de magnetotransport de films magnetiques granulaires." Paris 11, 1996. http://www.theses.fr/1996PA112324.

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L'ensemble de mon travail de these a ete consacre a la recherche de nouvelles methodes d'elaboration de materiaux magnetiques granulaires. Les deux solutions, que nous avons explorees, sont la fabrication d'agregats magnetiques par ejm et le depot d'agregats (initialement formes par une source a vaporisation laser) de faible energie (low energy cluster beam deposition). L'utilisation de la methode ejm pour l'obtention de films magnetiques granulaires passe par une etude systematique des mecanismes de nucleation et de croissance des metaux deposes sur le substrat. Dans le cas du systeme fe/cr, nous pouvons fabriquer des agregats de fer a la surface du tio#2(110) et l'interaction du chrome avec le tio#2(110), caracterisee par xps, permet de stabiliser une croissance quasi-bidimensionnelle des couches de chrome sur le tio#2. Par contre, en raison de vraisemblables problemes d'oxydation, nous n'avons pas reussi a obtenir des structures granulaires fe#xcr#1#-#x magnetoresistives. Par codeposition d'argent et de cobalt, nous avons elabore des couches co#xag#1#-#x tres minces (50 a) sur mgo(001). L'effet maximum de mr geante atteint 14% a 4,2 k dans des champs de saturation tres eleves (plus de 60 koe) pour l'echantillon contenant 14% de cobalt. Dans le systeme co#xag#1#-#x prepare par lecbd, nous avons montre le comportement superparamagnetique des agregats de cobalt pour des echantillons dont la concentration volumique de cobalt est inferieure a 15%. La mr geante presente le comportement attendu, augmentant avec la concentration d'agregats, presentant un maximum (12% a 4,2k) a 19% et diminuant ensuite en raison de couplages ferromagnetiques entre agregats. Les deviations observees au modele de zhang et levy dans le domaine des faibles concentrations magnetiques semblent indiquer que l'hypothese de self averaging de zhang et levy devient de plus en plus injustifiee quand les agregats sont relativement disperses

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44

Gauthier, Didier. "Magnetotransport sous pression hydrostatique dans le systeme gainas/inp." Toulouse, INSA, 1988. http://www.theses.fr/1988ISAT0016.

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45

Fisher, Ian Randal. "An experimental study of magnetotransport properties of several new superconductors." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/251609.

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46

Prasad, Rajesh Shyam. "Magnetotransport studies in N-Channel Si:SiGe modulation doped quantum wells." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309227.

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47

Bassom, Neil James. "Magnetotransport studies of space charge layers in narrow-gap semiconductors." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291070.

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Wang, Kaiyou. "Magnetotransport and magnetic properties of (Ga,Mn)As thin films." Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416733.

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Hayes, David Geoffrey. "Magneto-optical and magnetotransport studies of low dimensional semiconductor structures." Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314755.

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50

Tyler, André-William David. "An investigation into the magnetotransport properties of layered superconducting perovskites." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624684.

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Dissertations / Theses on the topic 'Magnetotransport'

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