Heusler alloy Mn₂CoAl: structural, magnetic and electronic properties

Abstract In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn 2 CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg 2 CuTi-type crystal structure of Mn 2 CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μ B at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn 2 CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn 2 CoAl.