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.

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Spintronics: Fundamentals and applications

Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

The manganese oxides of general formula RE1−xMxMnO3 (RE = rare earth, M = Ca, Sr, Ba, Pb) have remarkable interrelated structural, magnetic and transport properties induced by the mixed valence (3+–4+) of the Mn ions. In particular, they exhibit very large negative magnetoresistance, called colossal magnetoresistance (CMR), in the vicinity of metal–insulator transition for certain compositions. In this review paper, we summarize the most important features of the physics of the CMR manganites. The growth techniques for manganese oxide thin films, which are the basic material for potential applications, are reviewed and their structure and morphology examined in relation to growth parameters. The effects of epitaxial strains on the physical properties are discussed. Early works on superlattices and devices are presented.

http://iopscience.iop.org/article/10.1088/0022-3727/36/8/201/pdf

CMR manganites: physics, thin films and devices

Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics The most fundamental spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field

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Semiconductor Spintronics

We study theoretically the spin transport in a nonmagnetic metal connected to ferromagnetic injector and detector electrodes. We derive a general expression for the spin accumulation signal which covers from the metallic to the tunneling regime. This enables us to discuss recent controversy on spin injection and detection experiments. Extending the result to a superconducting device, we find that the spin accumulation signal is strongly enhanced by opening of the superconducting gap since a gapped superconductor is a low carrier system for spin transport but not for charge. The enhancement is also expected in semiconductor devices.

https://arxiv.org/pdf/cond-mat/0212317.pdf

Spin injection and detection in magnetic nanostructures

The critical current of a thin film of the high- ${T}_{c}$ superconductor ${\mathrm{DyBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$, when incorporated in a heterostructure in which it is separated from a ferromagnetic underlayer of ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_{3}$ by an undoped ultrathin ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}$ film, has been found to be strongly suppressed by current flowing in the ferromagnetic film. A control experiment with a Au film replacing the ferromagnet did not show such a response, and resistive heating was ruled out by additional measurements. The effect would appear to be caused by pair breaking associated with spin-polarized carriers being injected into the superconductor.

Critical Current Suppression in a Superconductor by Injection of Spin-Polarized Carriers from a Ferromagnet

Cuprate/manganite heterostructures

Since the discovery of giant magnetoresistance [1] andoscillatory interlayer coupling [2], metallic magnetic mul-tilayers have been the subject of intensive research [3].A physical picture of the coupling is provided in termsof quantum interference due to conﬁnement of electronsin the nonmagnetic spacers [4,5]. Ruderman-Kittel-Kasuya-Yosida (RKKY) theory [6], successfully used todescribe the eﬀect, appearsto be a limiting case of a moregeneral approach [5]. The prediction that oscillations pe-riods are determined by the extremal spanning vectors ofthe Fermi surface of the nonmagnetic spacer is now sup-ported by a wealth of experimental data [7]. The phaseand magnitude of the coupling oscillations apparently aresensitive to the interface matching of the electron bandsfor a particular magnetic conﬁgurationof the layers[3–5].While these eﬀects have been studied in many sim-ple metal and alloy systems, little progress has beenachieved in investigating them in multilayers consistingentirely of compounds [8]. In this Letter we report theﬁrst observation of oscillatory coupling in heterostruc-tures fabricated entirely of oxides, thus extending theﬁeld to a novel class of materials. The ferromagneticlayer material, barium-doped lanthanum manganese ox-ide La

Oscillatory exchange coupling and positive magnetoresistance in epitaxial oxide heterostructures

First-principles band structure calculations have been used to investigate epitaxially strained ${\mathrm{LaNiO}}_{3}$ films. Experimentally, tensile biaxial strain has been realized in pseudomorphic ${\mathrm{LaNiO}}_{3}$ films grown on ${\mathrm{SrTiO}}_{3}$ (001) substrates using ozone-assisted molecular beam epitaxy. Measured and calculated out-of-plane lattice parameters are in excellent agreement. This demonstrates the viability of the computational method as well as the high quality of the films.

Electronic and crystal structure of fully strained LaNiO 3 films

The voltage bias, temperature, and magnetic field dependence of the differential conductance of the interface between a half-metallic ferromagnet and a high-Tc superconductor have been studied in DyBa2Cu3O7/La2/3Ba1/3MnO3 heterostructures Below the superconducting transition the differential conductance exhibits a dip at zero bias whose amplitude is a decreasing function of temperature and/or magnetic field These results are interpreted qualitatively using a picture based on the suppression of Andreev reflection as a consequence of the high spin polarization of the carriers in the half-metallic ferromagnet

K. R. Nikolaev

Papers

Critical Current Suppression in a Superconductor by Injection of Spin-Polarized Carriers from a Ferromagnet

Cuprate/manganite heterostructures

Oscillatory exchange coupling and positive magnetoresistance in epitaxial oxide heterostructures

Electronic and crystal structure of fully strained LaNiO 3 films

Differential conductance of the ferromagnet/superconductor interface of DyBa2Cu3O7/La2/3Ba1/3MnO3 heterostructures