Conductance quantization and magnetoresistance in magnetic point contacts.
TL;DR: The magnetoresistance is strongly enhanced for the narrow PC and oscillates with the conductance and the sequence of quantized conductances depends on the relative orientation of magnetizations between left and right electrodes.
Abstract: We theoretically study the electron transport through a magnetic point contact (PC) with special attention given to the effect of an atomic scale domain wall (DW). The spin precession of a conduction electron is forbidden in such an atomic scale DW and the sequence of quantized conductances depends on the relative orientation of magnetizations between left and right electrodes. The magnetoresistance is strongly enhanced for the narrow PC and oscillates with the conductance.
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TL;DR: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems as discussed by the authors, where the primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport.
Abstract: Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.
9,158 citations
Cites background from "Conductance quantization and magnet..."
...This behavior, also known as ballistic magnetoresistance, has already been studied in a large number of materials and geometries (Bruno, 1999; Chung et al., 2002; Garcia et al., 1999; Imamura et al., 2000; Tatara et al., 1999; Versluijs et al., 2001)....
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...This behavior, also known as ballistic magnetoresistance, has already been studied in a large number of materials and geometries (Bruno, 1999; Garcia et al., 1999; Tatara et al., 1999; Imamura et al., 2000; Versluijs et al., 2001; Chung et al., 2002)....
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TL;DR: Spintronics is one of the emerging research fields in nanotechnology and has been growing very rapidly as mentioned in this paper, which has led to the discovery of giant magnetoresistance in 1988, which utilized spin-polarized electron transport across a non-magnetic metallic layer.
Abstract: Spintronics is one of the emerging research fields in nanotechnology and has been growing very rapidly. Studies of spintronics were started after the discovery of giant magnetoresistance in 1988, which utilized spin-polarized electron transport across a non-magnetic metallic layer. Within 10 years, this discovery had been implemented into hard disk drives, the most common storage media, followed by recognition through the award of the Nobel Prize for Physics 19 years later. We have never experienced such fast development in any scientific field. Spintronics research is now moving into second-generation spin dynamics and beyond. In this review, we first examine the historical advances in spintronics together with the background physics, and then describe major device applications.
405 citations
TL;DR: In this article, the authors investigated the domain wall dynamics induced by electric current based on the $s$-$d$ exchange model, where the wall is treated as rigid and planar and is described by two collective coordinates.
Abstract: This review describes in detail the essential techniques used in microscopic theories on spintronics. We have investigated the domain wall dynamics induced by electric current based on the $s$-$d$ exchange model. The domain wall is treated as rigid and planar and is described by two collective coordinates: the position and angle of wall magnetization. The effect of conduction electrons on the domain wall dynamics is calculated in the case of slowly varying spin structure (close to the adiabatic limit) by use of a gauge transformation. The spin-transfer torque and force on the wall are expressed by Feynman diagrams and calculated systematically using non-equilibrium Green's functions, treating electrons fully quantum mechanically. The wall dynamics is discussed based on two coupled equations of motion derived for two collective coordinates. The force is related to electron transport properties, resistivity, and the Hall effect. Effect of conduction electron spin relaxation on the torque and wall dynamics is also studied.
274 citations
TL;DR: In this paper, the authors investigated the domain wall dynamics induced by an electric current, based on the s − d exchange model, and derived coupled equations of motion derived for two collective coordinates.
274 citations
TL;DR: In this paper, the physics of giant magneto resistance (GMR) were discussed and the role of the spin-polarized electronic band structure was emphasized for understanding GMR.
Abstract: Publisher Summary This chapter discusses the physics of giant magneto resistance (GMR). The chapter emphasizes the role of the spin-polarized electronic band structure that is crucial for understanding GMR. The origin of GMR and a simple resistor model has been introduced in the chapter. The experimental data on current-in-the-plane (CIP) GMR in magnetic multilayers, spin valves, dependence of GMR on composition, layer thickness, roughness, impurities, outer boundaries, and temperature have also been discussed in the chapter. The theoretical formulations of GMR within free electron and simple tight-binding models have been reviewed from the semiclassical and quantum mechanical viewpoints. Multiband models for GMR have also been reviewed. The semiclassical and quantum mechanical approaches to GMR within the diffusive limit and the interpretation of selected experimental results have been presented in the chapter.
266 citations