First-principles study for electronic structure and physical property of Co-based Heusler alloys

Abstract

Abstract.The statistical investigation of the physical property of Co-based Heusler alloys with the atomic composition or configuration dependence are carried out in first-principles approach. In particular, the electronic structure, magnetic moment and electrical resistivity due to disorder alloy effects of Co2MnAl1−zSiz (0.0 < z < 1.0) and Co2Mn1−yFeySi (0.0 < y < 1.0) with the L21, B2 and A2 structure are calculated by using the tight-binding linear muffin-tin orbital method combined with the coherent potential approximation based on the local spindensity functional approximation and by using the Kubo-Greenwood formula, respectively. The obtained results indicate that these properties of the Co-based Heusler alloys significantly depend on the atomic configuration and composition, especially, they are sensitive to the existence of the half-metallic property.

Magnetization dynamics of a CoFe/Co2MnSi magnetic bilayer structure

“…There are two commonly observed phases in epitaxially grown CMS crystals-L2 1 and B2 phases-that are known to exhibit halfmetallic behavior. 26 Unlike the L2 1 phase, where the Mn and Si atoms are highly ordered, Mn and Si atoms are randomly located at lattice points in the cubic unit cell in the B2 phase. To determine which phase of CMS was grown, we attempted to obtain pole figures and θ À 2θ scans about the expected positions of the CMS (111) peak, but we were unable to find such a peak.…”

“…25 By controlling the annealing temperature, CMS alloys can also crystallize in the B2 phase, which is half-metallic as well. 26 Indeed, excellent static behavior, including a TMR ratio of 570% at low temperature in a CMS/AlO/CMS structure 27 and 753% in a CMS/MgO/CoFe structure, 22 has been demonstrated. The crucially important interface quality between CMS and the tunneling oxide can be improved with a thin intermediate layer based on cobalt iron (e.g., CoFeB), resulting in TMR ratios as high as 222% at room temperature.…”

Co2MnSi Heusler alloy as an enhancing layer of perpendicular magnetic anisotropy for MgO-based magnetic tunnel junctions with L10 ordered FePd

“…20) The B2 CMS has known to have a spin polarization of 100%. 21) However, it seems difficult to adapt their method for decreasing critical switching current and for mass production because of the thick CoPt and the complex thermal process. Here, we attempt to fabricate an ultra-thin L1 0 FePd= B2 CMS bilayer by annealing just once at 400 °C in order to have both strong PMA and high spin polarization, and we investigated the effect of changes in the thickness of ultrathin CMS layer inserted between FePd and MgO on the structural and magnetic properties.…”