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.

  • Source
    [Show abstract] [Hide abstract]
    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)
    physica status solidi (RRL) - Rapid Research Letters 10/2007; 1(5). · 2.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    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.
    Journal of Magnetism and Magnetic Materials 02/2014; 354. · 2.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We investigated the effect of nonstoichiometry on the half-metallic character of the Heusler alloy Co2MnSi (CMS) through the Mn composition (α) dependence of the saturation magnetization per formula unit (μs) of Co2MnαSiβ thin films and the tunneling magnetoresistance (TMR) ratio of CMS/MgO/CMS magnetic tunnel junctions (CMS MTJs) having Co2MnαSiβ electrodes. As a basis for understanding the effect of nonstoichiometry in CMS, we developed a generalized form of the site-specific formula unit (SSFU) composition model, which assumes the formation of only antisite defects, not vacancies, to accommodate nonstoichiometry. The α dependence of μs was well explained by density functional calculations with the coherent potential approximation based on the SSFU composition model for α up to a certain critical value (αc)>1.0. The μs data for Mn-deficient films deviated from the Slater-Pauling predicted data for half-metals due to Co atoms at the nominal Mn sites (CoMn). The theoretical spin polarizations, obtained from only the s- and p-orbital components, Pth(sp), were found to qualitatively explain the α dependence of the TMR ratio except for α > αc. This is in contrast to the theoretical spin polarizations obtained from the s-, p-, and d-orbital components, Pth(spd). A decrease in the TMR ratio observed for CMS MTJs having Mn-deficient electrodes was ascribed to small s- and p-orbital components of the local density of minority-spin in-gap states at the Fermi level that appeared for both antisite CoMn atoms and Co atoms at the regular sites.
    Physical Review B 12/2013; 89(1). · 3.66 Impact Factor

Full-text (3 Sources)

Available from
Jun 3, 2014