Investigation of the half-metallicity, magnetism and spin transport properties of double half-Heusler alloys Mn2CoCrZ2 (Z = P, As)

Abstract

A new subfamily of Heusler alloys, i.e. double half-Heusler alloys Mn₂CoCrZ₂ (Z = P, As), are investigated by employing density functional theory combined with the nonequilibrium Green's function. The calculations of their magnetic properties reveal that Mn₂CoCrZ₂ (Z = P, As) are half-metallic ferrimagnets. Mn₂CoCrP₂ possesses an indirect spin-down bandgap of 0.671 eV and maintains half-metallicity with the lattice constant ratio c/a ranging from 1.72 to 2.40, while Mn₂CoCrAs₂ owns a direct spin-down bandgap of 0.993 eV and maintains half-metallicity with c/a ranging from 1.5 to 2.5. By employing Mn₂CoCrZ₂ as the electrodes and GaAs as the tunnel barrier, two kinds of magnetic tunnel junctions (MTJs) are constructed. When two electrodes of MTJs are in parallel magnetic configuration, the spin-up electrons have strong transmission ability, while the transmission ability of spin-down electrons is severely suppressed. When two electrodes of MTJs are in antiparallel magnetic configuration, the transmission ability of both spin-channel electrons is suppressed. The calculated tunnel magnetoresistance ratios of Mn₂CoCrP₂/GaAs/Mn₂CoCrP₂ and Mn₂CoCrAs₂/GaAs/Mn₂CoCrAs₂ MTJs reach up to 7.96 × 10⁸ and 1.85 × 10⁸, respectively, indicating that they are promising candidates for high performance spintronic devices.