Ferromagnetism and stability of half-metallic MnSb and MnBi in the strained zinc-blende structure: Predictions from full potential and pseudopotential calculations

We use first principles calculations to study the energy and magnetic moment of MnSb and MnBi in the (equilibrium) nickel arsenide, zinc-blende, and tetragonally distorted zinc-blende structures. We find that the zinc-blende structure is mechanically unstable, i.e., the energy is a relative maximum for c/a=1 at fixed volume. We studied the tetragonal structures by fixing the in-plane lattice constant to be equal to that of typical semiconductors (such as GaAs) which might serve as substrates for epitaxial growth and then minimizing the energy as a function of c/a. Over a wide range of a, including that of GaAs, we find half-metallic ferromagnets. We suggest that these structures are much more likely to be achieved as thin films than the cubic zinc-blende phases.