@phdthesis{oai:sucra.repo.nii.ac.jp:00019383,
 author = {AKTAR, MST SANJIDA},
 month = {},
 note = {vii, 74p, A theoretical aspect of entropy production rate in ambipolar conductors has been presented. As joule heating addresses the issue of entropy production in spin Hall geometry, we have evaluated the role of spin current in the energy dissipation mechanism in ambipolar conductors with identical spin-related characteristics between holes and electrons. Since spin injection induces imbalance between up and down spin chemical potentials, application of the Gibbs-Duhem ）GD） relation to ambipolar conductors establishes a thermodynamic relation between the spin-dependent chemical potentials of holes and electrons, inducing an asymmetric spin splitting between the hole and electron chemical potentials. This yields two types of spin relaxation as in ambipolar conductors two modes of spin currents are present namely parallel and antiparallel spin current. The GD relation allow the antiparallel spin current, where hole and electron spins flow in the opposite direction, to have a large spin diffusion length, but to retain that of the parallel spin current at a standard value.

A long lifetime as well as a large distance in spin coherence are desirable for spintronics devices because spatially and temporally large spin coherence makes spin manipulation easier. We propose a Baber-type collision in nearly compensated metals which reveals extraordinarily large spin relaxation time ）Ts） associated with the antiparallel spin current. A theoretical study on the spin and charge transports in nearly compensated metals shows that i） antiparallel spin current satisfies the Onsager reciprocal relation in combination with conventional charge current and ii） both the longitudinal and Hall resistivities are influenced by the enhancement of spin relaxation time ）Ts）. The resistivities are characterized in terms of two specific mechanisms, i.e., conventional Hall effect and the resonance Hall effect. It is also shown that the resonance Hall effect is coupled to a sustaining mode of antiparallel spin current. These findings convince that nearly compensated metals have potential for being used as spintronics materials., Chapter 1: Introduction
1.1 General Spintronics…………………………………………… 1
1.2 Motivation of the Research…………………………………… 3
1.3 Introduction to Ambipolar conductors……………………… 7
1.4 Orientation of the thesis……………………………………… 7

Chapter 2: Fundamental aspects of Spin transport
2.1 Introduction……………………………………………………… 9
2.2 Ferromagnetism: Source of spin polarized current……………… 10
2.3 Electrochemical potential………………………………………… 12
2.4 The model of Spin transport in hybrid nanostructure……………… 13
2.4.1 Spin injection…………………………………………… 13
2.4.2 Spin accumulation………………………………………… 14
2.4.3 Spin detection…………………………………………… 18

Chapter 3: Theoretical evaluation of entropy production rate in ambipolar conductors
3.1 Introduction……………………………………………………… 19
3.2 Derivation of entropy production rate equation…………………… 20
3.3 Application of spherical Fermi surface to entropy production rate equation………………………………………………… 33
3.4 Significance of entropy production rate equation in ambipolar conductors…………………………………………………… 34
3.5 Antiparallel spin polarization between hole and electron………… 34
3.6 Summary…………………………………………………………… 37

Chapter 4: Spin relaxation mechanism and enhancement of spin coherence in nearly compensated metals
4.1 Effect of the Baber-type collision on spin relaxation time………… 38
4.2 Quantitative evaluation of spin diffusion length of ambipolar conductors…………………………………………………… 43
4.3 External control of charge polarization…………………………… 45
4.4 Summary…………………………………………………………… 46

Chapter 5: Spin and charge transport in nearly compensated metals
5.1 Relationships between charge-spin flows and their thermodynamic forces in nearly CM…………………………………… 47
5.2 Derivation of diagonal and off-diagonal parts of resistivity………… 52
5.3 Mechanism of resonance Hall effect………………………………… 58
5.4 Summary…………………………………………………………… 64

Chapter 6: Conclusion…………………………………………………………………………… 65

References…………………………………………………………………………………………… 67, 指導教員 : 酒井政道, text, application/pdf},
 school = {埼玉大学},
 title = {A theoretical study on spin-charge coupled transport and entropy production characteristics in nearly compensated metals},
 year = {2020},
 yomi = {アクタル, エムエスティ サンジーダ}
}