Stability and magnetic properties of Mn-substituted ScN from first principles

We present a spin density functional theory (DFT) study for semiconducting ScN and Mn-substituted ScN. Their structural and magnetic properties have been investigated using the all electrons augmented spherical wave method (ASW) with a generalized gradient GGA functional for treating the effects of exchange and correlation. Band structure calculations show that ScN is semiconductor with a narrow indirect band gap $\Gamma$-X of 0.54 eV. The total-energy versus volume calculations show that ternary Sc$_{0.75}$Mn$_{0.25}$N nitride is more stable in face centered tetragonal-rocksalt (fct-rocksalt) structure, found experimentally, than the cubic rocksalt one. Spin polarized results, at theoretical equilibrium, indicate that the ground state of Sc$_{0.75}$Mn$_{0.25}$N is ferromagnetic with a high moment at Mn-atom (3.44$\mu_B$), and zero moment on Sc and N ones. The magnetovolume effects of Mn-substitution in ScN lattice are discussed. The electronic structures analyzed from site/spin projected density of states and chemical bonding, for both the mononitride and the ternary alloy, are reported. A discussion of the structural and magnetic properties of Sc$_{0.75}$Mn$_{0.25}$N is given with a comparison to ScN, in order to get insights of the Mn-substitution effects.