Half-Metallic Materials and Their Properties

Abstract

PrefaceSince the first theoretical prediction of a half-metallic material -one in which the electrons of one spin participate in conduction while those of the other do not -was published in 1983, much effort has been exerted to understand, predict, and grow new half-metallic materials. A main impetus for this effort has been the great potential for half-metals (HMs) in spintronics -a new generation of electronics in which the electron spin, as well as its charge, is exploited to achieve substantial reductions in size and/or improvements in performance. In an HM, the electrons of one spin channel are metallic while those of the other are insulating, the spin polarization at Fermi level is complete (100%), and the magnetic moment is an integer. Partially spin-polarized spintronic materials, such as Co/Fe layered structures, have already led to breakthroughs in information storage and processing technologies, such as magnetoresistance (MR)-based read heads, magnetic random access memory (MRAM), and spin-current switches. Because HMs exhibit very large (ideally, infinite) MRs, it is not surprising that the design and realization of HM devices have been among the hottest topics in condensed matter physics and materials science in recent years.Tremendous theoretical, experimental, and technological progress in the understanding of half-metallic materials has been achieved in the past few years, and the scientific literature has grown correspondingly. It is opportune, therefore, to summarize the main concepts, results, and advances in order to spark and facilitate new research and provide a solid and coherent foundation for new researchers in this exciting field. These are the goals we set out to achieve in the present monograph, at a level appropriate for advanced undergraduate or graduate students in physics, chemistry, and materials science.In the introductory chapter, we give an overview of the main features, similarities, and differences among the three main classes of HMs which have emerged to date. We discuss key features from both a theoretical Half-metallic Materials and Their Propertiesand technological point of view. We emphasize the three basic interactions underlying half-metallic properties in all such materials in the hope that new half-metallic materials may be realized by tuning each of the interactions independently. For device applications, it is necessary to understand both electronic and magnetic properties. Substantial progress has been achieved both experimentally and theoretically in the endeavor to understand and predict the properties of half-metallic materials. In Chapter 2, we provide a discussion of the key experimental and theoretical techniques, as appropriate for each class of material, which have been employed to date in order to achieve that understanding and predictive capability. The three main classes of half-metallic materials that have emerged to date are: (i) the Heusler alloys; (ii) transition-metal oxides; and (iii) pnictides, chalcogenides, and carbides with the zincblende (...

Interface-induced phenomena in magnetism

“…The wealth of discoveries in these metallic systems stimulated investigation of magnetic heterostructures based on other constituents, including magnetic semiconductors and oxides. The latter includes binary oxides (see for example the large bodies of work on Fe 3 O 4 , CrO 2 [Fong et al ., 2013], V-O insulator-to-metal transition systems [de la Venta et al ., 2014], artificially-structured magnetic semiconductors using CoO/ZnO multilayers [Lee et al ., 2013a], or EuO [Coey et al ., 1999]), but a wealth of remarkable behavior is found in complex oxides, concurrent with a general rise in interest in heterostructures and interfaces of these materials [Ramesh and Schlom, 2008; Chakalian et al ., 2012; Hwang et al ., 2012; Bhattacharya and May, 2014; Stemmer and Allen, 2014, Sulpizio et al ., 2014]. We provide a brief review, focusing on the perovskite structure magnetic oxides that serve as model systems.…”

Prediction of half-metallicity and spin-gapless semiconducting behavior in the new series of FeCr-based quaternary Heusler alloys: an ab initio study

“…High temperature makes these devices suitable for room temperature applications. [1][2][3]. The possibility of the implementation of these compounds in real spintronics devices and the major challenges have been discussed in the literature [4][5][6].…”

Spintronic properties of Li1.5Mn0.5Z (Z=As, Sb) compounds in the Cu2Sb structure

“…In the cubic structures, such as full-Heusler, HH and ZB alloys with TM elements, the desired magnetic properties, in particular half-metallicity, are a consequence of three competing mechanisms [6]: (a) the crystal field splits the d-states of TM elements into triply-and doubly-degenerate states. (b) The triply degenerate states and the sp [3] orbitals of the neighboring non-metal element hybridize to form a gap between bonding and anti-bonding states.…”

“…The Slater-Pauling-Kübler rule [14] and the ionic model [15] have successfully been used to predict the magnetic moments of full-and half-Heusler alloys [5][6][7][8] as well as other half-metals [13] if the predicted values are positive. Can the rule and the model predict values of the moment of any Li 3 MnV 2 calculated results, so that the future selection of elements that form Cu 2 Sb structure alloys can be fruitful?…”