Effect of doping and disorder on the half-metallicity of full Heusler alloy

Department of Materials Science, School of Natural Sciences, University of Patras, GR-26504 Patra, Greece
Applied Physics Letters (Impact Factor: 3.52). 03/2006; DOI: 10.1063/1.2235913
Source: arXiv

ABSTRACT Heusler alloys containing Co and Mn are amongst the most heavily studied half-metallic ferromagnets for future applications in spintronics. Using state-of-the-art electronic structure calculations, we investigate the effect of doping and disorder on their electronic and magnetic properties. Small degrees of doping by substituting Fe or Cr for Mn scarcely affect the half-metallicity. A similar effect is also achieved by mixing the sublattices occupied by the Mn and sp atoms. Thus the half-metallicity is a robust property of these alloys.

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    ABSTRACT: The magnetic ordering and its effect on the physical stability of X2Mn1+xSn1−x (0≤x≤0.5, and X=Ru, Os, Co, Rh, Ni, Pd, Cu, and Ag) Heusler alloys are investigated systematically by the use of first-principles method. It is found that the ferromagnetic (FM) coupling between Mn on Mn sublattice (Mn1) and Mn on Sn sublattice (Mn2) is favorable over the antiferromagnetic (AFM) coupling for X with the number of valence electrons [Nv(X)] of 8 and 9, and vice versa for X with Nv(X)=10 and 11, originated from the competition of the exchange interactions between X-Mn2 and Mn1-Mn2. In comparison with the FM Mn1-Mn2 coupling, the AFM coupling decreases significantly the shear elastic constant C′ but increases slightly C44, which results in increasing elastic anisotropy (A=C44/C′) and consequently may facilitate the tetragonal shear lattice deformation. The hybridization of the minority electronic states between X d and Sn p plays a dominant role on the orientation of the magnetic coupling. The smaller change of the density of states in the Fermi level, induced by the lattice distortion for C′, corresponds to the softer C′ as well as the larger A in the AFM state than the FM one.
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    ABSTRACT: Ferromagnetic full Heusler alloys containing Co are amongst the most studied half-metallic systems. Several studies recently have been concentrated on the effect of defects and impurities. We focus in this Letter on the case of vacancies in these alloys. We show that the occurrence of vacancies at the sites occupied by Co atoms can destroy half-metallicity and alters the Slater–Pauling rule. Such defects are likely to occur since they result to the C1b lattice structure of the semi-Heusler alloys. Contrary, the appearance of vacancies at the other sites keeps the half-metallic character of the parent alloys. Thus for realistic devices it is important to prevent the appearance of vacancies during the growth of thin films. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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    ABSTRACT: We investigate the effect of doping and disorder of Ti2CoNixInSny (x, y=0.0, 0.25, 0.50, 0.75, 1.00) employing the virtual crystal approximation. The results show that all alloys under study are half-metals, and their total spin moments follow the so-called Slater-Pauling behavior of the ideal half-metallic systems. Especially, we concentrate on the properties related to the spin-flip gap and the density of states at the Fermi level, and present the possibility to engineer the properties by changing the relative concentrations of the transition metal and sp atoms in a way of dope or disorder. In realistic applications, the spin-flip gap and the density of states at the Fermi level are needed for large values of the perfectly spin-polarized current in spintronic devices such as spin valves or magnetic tunnel junctions. In the manuscript, the properties with respect to the different transition metal and sp atoms concentrations are provided, which offers a choice to obtain ideal half-metallicity in spintronics device applications.

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