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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

EXPERIMENTAL STUDIES OF QUANTUM MECHANICAL INTERFERENCE EFFECTS IN MAGNETORESISTANCE OF SINGLE CRYSTALS OF ULTRAPURE MAGNESIUM

Sandesara, Niranjan Bhogilal January 1980 (has links)
New types of quantum interference oscillations in transverse magnetoresistance of single crystals of ultrapure magnesium are reported. These oscillations occur as a function of the angle of rotation when the current is passed along the [112̄0] direction and the magnetic field H(→) is rotated by ≲ 1° from [101̄0] towards the [0001] symmetry axis. In order to characterize the oscillations, extensive qualitative data were taken for fields up to 24 kG and for temperatures in the range of 1.4 K-4.2 K. It is shown that these angle-dependent oscillations have the same origin as the field-dependent interferometer oscillations first reported by Stark and Friedberg. Both types of oscillations arise from the electron quantum states on the coupled orbit network, which is obtained for H(→)∥[1010]. It is shown that high sensitivity of the oscillations and the background magnetoresistance (for H within →1° from [101̄0] to field inhomogeneity and crystal strain yields strong evidence for a new regime of quantum transport. In this regime, quantum phase coherence of the electrons extends over distances of the order of 0.1 mm, and coherence determines not only the oscillation amplitudes but also the background. The "stacked mirror" model of Stark and Reifenberger is not applicable in such a regime of transport. A rudimentary model is presented that seems to be in qualitative agreement with the data. However, band structure calculations firmly establish that the large oscillations arise from the symmetry breaking of the two interferometer lobes as the field is rotated away from [101̄0].
62

An investigation of magnetically active terahertz devices

Straatsma, Cameron J. E. Unknown Date
No description available.
63

Quantum corrections to the conductivity in simple metallic glasses

Richter, Reinhart January 1988 (has links)
The validity of the theories of quantum corrections to the electrical conductivity, namely weak localization and enhanced electron-electron interaction, has been tested quantitatively in well characterized, free-electron-like Mg-Cu and Mg-Zn metallic glasses containing various amounts of Ag and Au through measurement of the electrical resistivity between 1.5K and 20K in magnetic fields up to 5.6T. It is found that the theories give an excellent description of the magnetoresistance at low fields, in both the weak and strong spin-orbit scattering limit but that at higher fields they break down. The electron spin-orbit scattering and dephasing rates have been deduced. Above 4K the dephasing rate is controlled by inelastic electron-phonon scattering, below 4K it saturates to a value consistent with a new model of dephasing of the quantum back scattering interference by ionic zero-point motion. The first direct measurement of the effect of superconductivity on the magnetoresistance in bulk amorphous metals is also presented. The temperature dependence of the resistivity between 1.5 and 6K is in qualitative but not quantitative agreement with the quantum correction theories.
64

Giant magnetoresistance and quantum transport in magnetic hybrid nanostructures

Sanvito, Stefano January 1999 (has links)
No description available.
65

Rectifying characteristics, photovoltaic effect and magnetoresistance in heterojunctions composed of manganite and titanate

Luo, Zhi, January 2008 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references. Also available in print.
66

Spintronics with metals current perpendicular-to-the-plane magneto-transport studies in metallic multilayers and nanopillars /

Sharma, Amit. January 2008 (has links)
Thesis (PH.D.)--Michigan State University. Physics, 2008. / Title from PDF t.p. (viewed on Aug. 11, 2009) Includes bibliographical references (p. 156-164). Also issued in print.
67

Spin-dependent transport phenomena in organic semiconductors

Bergeson, Jeremy D. January 2007 (has links)
Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request
68

Scattering Effect on Anomalous Hall Effect in Ferromagnetic Transition Metals

Zhang, Qiang 30 November 2017 (has links)
The anomalous Hall effect (AHE) has been discovered for over a century, but its origin is still highly controversial theoretically and experimentally. In this study, we investigated the scattering effect on the AHE for both exploring the underlying physics and technical applications. We prepared Cox(MgO)100-x granular thin films with different Co volume fraction (34≤x≤100) and studied the interfacial scattering effect on the AHE. The STEM HAADF images confirmed the inhomogeneous granular structure of the samples. As x decreases from 100 to 34, the values of longitudinal resistivity (pxx) and anomalous Hall resistivity (pAHE) respectively increase by about four and three orders in magnitude. The linear scaling relation between the anomalous Hall coefficient (Rs) and the pxx measured at 5 K holds in both the as-prepared and annealed samples, which suggests a skew scattering dominated mechanism in Cox(MgO)100-x granular thin films. We prepared (Fe36/n/Au12/n)n, (Ni36/n/Au12/n)n and (Ta12/n/Fe36/n)n multilayers to study the interfacial scattering effect on the AHE. The multilayer structures were characterized by the XRR spectra and TEM images of cross-sections. For the three serials of multilayers, both the pxx and pAHE increase with n, which clearly shows interfacial scattering effect. The intrinsic contribution decreases with n increases in the three serials of samples, which may be due to the crystallinity decaying or the finite size effect. In the (Fe36/n/Au12/n)n samples, the side-jump contribution increases with nn, which suggests an interfacial scattering-enhanced side jump. In the (Ni36/n/Au12/n)n samples, the side-jump contribution decreases with n increases, which could be explained by the opposite sign of the interfacial scattering and grain boundary scattering contributed side jump. In the (Ta12/n/Fe36/n)n multilayers, the side-jump contribution changed from negative to positive, which is also because of the opposite sign of the interfacial scattering and grain boundary scattering contributed side jump. The interfacial scattering effect on the AHE is much more complicated than surface scattering in thin films or scattering by delta-impurities in bulk-like samples.
69

Quantum corrections to the conductivity in simple metallic glasses

Richter, Reinhart January 1988 (has links)
No description available.
70

X-ray reflectivity study of GMR and porous silicon thin layers

Asgharizadeh, Saeid January 2007 (has links)
No description available.

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