Magnetoresistance in excess of 200% in ballistic ni nanocontacts at room temperature and 100 oe
TL;DR: In this paper, magnetoresistance experiments in magnetic Ni nanocontacts in the ballistic transport regime at room temperature were conducted and it was shown that the magnetoreduction for a few-atom contact reaches values of $280%$ at room-temperature and for applied magnetic fields of 100 Oe.
Abstract: We present magnetoresistance experiments in magnetic Ni nanocontacts in the ballistic transport regime at room temperature. It is shown that the magnetoresistance for a few-atom contact reaches values of $280%$ at room temperature and for applied magnetic fields of 100 Oe. Results are presented for over 50 samples showing the trend that the smaller the contact the larger the magnetoresistance response. This indicates that the effect arises just at the nanocontact.
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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 "Magnetoresistance in excess of 200%..."
...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: In this article, the authors discuss the results in the context of related developments, including Andreev reflection, shot noise, conductance quantization and dynamical Coulomb blockade.
1,346 citations
Cites background from "Magnetoresistance in excess of 200%..."
...[231] have produced stable atomic-sized Ni contacts at room temperature by embedding the contact between two Ni wires in a resin....
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TL;DR: In this article, the experimental status of multiferroics has been presented for both the bulk single phase and the thin film form, and a detailed overview on multiferromagnetic thin films grown artificially (multilayers and nanocomposites) is presented.
Abstract: Complex perovskite oxides exhibit a rich spectrum of properties, including magnetism, ferroelectricity, strongly correlated electron behaviour, superconductivity and magnetoresistance, which have been research areas of great interest among the scientific and technological community for decades. There exist very few materials which exhibit multiple functional properties; one such class of materials is called the multiferroics. Multiferroics are interesting because they exhibit simultaneously ferromagnetic and ferroelectric polarizations and a coupling between them. Due to the nontrivial lattice coupling between the magnetic and electronic domains (the magnetoelectric effect), the magnetic polarization can be switched by applying an electric field; likewise the ferroelectric polarization can be switched by applying a magnetic field. As a consequence, multiferroics offer rich physics and novel devices concepts, which have recently become of great interest to researchers. In this review article the recent experimental status, for both the bulk single phase and the thin film form, has been presented. Current studies on the ceramic compounds in the bulk form including Bi(Fe,Mn)O3, REMnO3 andthe series of REMn2O5 single crystals (RE = rare earth) are discussed in the first section and a detailed overview on multiferroic thin films grown artificially (multilayers and nanocomposites) is presented in the second section.
601 citations
TL;DR: The SMEAGOL algorithm as discussed by the authors constructs surface Green's functions describing the currentvoltage probes, which can be used to evaluate the I-V characteristics of atomic junctions, which integrates the nonequilibrium Green's function method with density functional theory.
Abstract: Ab initio computational methods for electronic transport in nanoscaled systems are an invaluable tool for the design of quantum devices. We have developed a flexible and efficient algorithm for evaluating I-V characteristics of atomic junctions, which integrates the nonequilibrium Green’s function method with density functional theory. This is currently implemented in the package SMEAGOL. The heart of SMEAGOL is our scheme for constructing the surface Green’s functions describing the current-voltage probes. It consists of a direct summation of both open and closed scattering channels together with a regularization procedure of the Hamiltonian and provides great improvements over standard recursive methods. In particular it allows us to tackle material systems with complicated electronic structures, such as magnetic transition metals. Here we present a detailed description of SMEAGOL together with an extensive range of applications relevant for the two burgeoning fields of spin and molecular electronics.
564 citations
TL;DR: In this article, the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic moment and magnetic anisotropies change markedly in ultrathin films as compared with their bulk counterparts, and to emphasize the role of atomic scale structure, strain and crystallinity in determining the magnetic properties.
Abstract: In this paper, we review some of the key concepts in ultrathin film magnetism which underpin nanomagnetism. We survey the results of recent experimental and theoretical studies of well characterized epitaxial structures based on Fe, Co and Ni to illustrate how intrinsic fundamental properties such as the magnetic exchange interactions, magnetic moment and magnetic anisotropies change markedly in ultrathin films as compared with their bulk counterparts, and to emphasize the role of atomic scale structure, strain and crystallinity in determining the magnetic properties. After introducing the key length scales in magnetism, we describe the 2D magnetic phase transition and survey studies of the thickness dependent Curie temperature and the critical exponents which characterize the paramagnetic–ferromagnetic phase transition. We next discuss recent experimental and theoretical results on the determination of the exchange constant, followed by an overview of measurements of the magnetic moment in the elemental 3d transition metal thin films in the various crystal phases that have been successfully stabilized, thereby illustrating the sensitivity of the magnetic moment to the local symmetry and to the atomic environment. Finally, we discuss briefly the magnetic anisotropies of Fe, Co and Ni in the fcc crystalline phase, to emphasize the role of structure and the details of the interface in influencing the magnetic properties. The dramatic effect that adsorbates can have on the magnetic anisotropies of thin magnetic films is also discussed. Our survey demonstrates that the fundamental properties, namely, the magnetic moment and magnetic anisotropies of ultrathin films have dramatically different behaviour compared with those of the bulk while the comparable size of the structural and magnetic contributions to the total energy of ultrathin structures results in an exquisitely sensitive dependence of the magnetic properties on the film structure.
516 citations