Theory of Mn-Based High-Magnetization Alloys

The realization of the magnetic moment of Mn atoms in ferromagnetic alloys is investigated theoretically. This paper is partly motivated by the recent discovery of high-magnetization Fe-Co-Mn thin films by Snow et al., who reported moments of up to 3.25 μ
_B
per atom. Structural and strain effects are discussed with particular emphasis on the distinction between tetragonal martensitic lattice distortions and Bain transitions in body-centered cubic, CsCl, and Heusler alloys. It is outlined how these lattice distortions affect the electronic structure of the alloys, and ab initio calculations are used to determine the net moment of cubic Fe
₆
Co
₆₃
Mn
₃₁
. The calculated moment, 2.90 μ
_B
per atom, is reasonably close to the experimental value.