21 research outputs found

    Effect of substitutional doping and disorder on the phase stability, magnetism, and half-metallicity of Heusler alloys

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    Spintronics is the fast growing field that will play a key role in optimizing power consumption, memory, and processing capabilities of nanoelectronic devices. Heusler alloys are potential candidates for application in spintronics due to their room temperature (RT) half-metallicity, high Curie temperature, low lattice mismatch with most substrates, and strong control on electronic density of states at Fermi level. In this work, we investigate the effect of {substitutional doping and disorder} on the half-metallicity, phase stability, and magnetism of Heusler alloys using density functional theory methods. Our study shows that electronic and magnetic properties of half/full-Heusler alloys can be tuned by changing electron-count through controlled variation of chemical compositions of alloying elements. We provide a detailed discussion on the effect of substitutional doping and disorder on the tunability of half-metallic nature of Co2_{2}MnX and NiMnX based Heusler alloys, where X represents group 13\textendash 16 and period 3\textendash 6 elements of the periodic table. {Based on the idea of electron count and disorder, we predicted a possible existence of thermodynamically stable half-metallic multicomponent bismuthides, for example, (CuNi3_{3})Mn4_{4}Bi4_{4} and (ZnNi7_{7})Mn8_{8}Bi8_{8}, through substitution doping at Ni site by specific Cu and Zn composition in half-Heusler NiMnBi.} We believe that the design guide {based on electron-counts} presented for half-metals will play a key role in electronic-structure engineering of novel Heusler alloys for spintronic application, which will accelerate the development and synthesis of novel materials.Comment: 19 pages (15 main text, 4 supplement) 9 Figures (6 main text, 3 supplement). arXiv admin note: substantial text overlap with arXiv:2004.0623

    Reliable First-Principles Alloy Thermodynamics via Truncated Cluster Expansions

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    In alloys cluster expansions (CE) are increasingly used to combine first-principles electronic-structure and Monte Carlo methods to predict thermodynamic properties. As a basis-set expansion in terms of lattice geometrical clusters and effective cluster interactions, the CE is exact if infinite, but is tractable only if truncated. Yet until now a truncation procedure was not well-defined and did not guarantee a reliable truncated CE. We present an optimal truncation procedure for CE basis sets that provides reliable thermodynamics. We then exemplify its importance in Ni3_3V, where the CE has failed unpredictably, and now show agreement to a range of measured values, predict new low-energy structures, and explain the cause of previous failures.Comment: 4 pages, 2 figure

    Stable atomic structure of NiTi austenite

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