Electronic, magnetic, and structural properties of CoVMnSb: ab initio study

We present results of a computational study of electronic, magnetic, and structural properties of CoVMnSb, a quaternary Heusler alloy. Our calculations indicate that this compound may crystallize in two energetically close structural phases: inverted and regular cubic. The inverted cubic phase is the ground state, with ferromagnetic alignment, and around 80% spin polarization. Despite having a relatively large band gap in the minority-spin channel close to the Fermi level, this phase does not undergo a half-metallic transition under pressure. At the same time, the regular cubic phase is half-metallic, and retains its perfect spin polarization under a wide range of mechanical strain. Transition to regular cubic phase may be attained by applying uniform pressure (but not biaxial strain). In practice, this pressure may be realized by atomic substitution of non-magnetic atom (Sb) with another non-magnetic atom (Si) of smaller radius. Our calculations indicate that 25% substitution of Sb with Si results in half-metallic regular cubic phase being the ground state. In addition, CoVMnSb_0.5Si_0.5 retains its half-metallic properties under a considerable range of mechanical pressure, thus making it attractive for potential spintronic applications. We hope that the presented results will stimulate experimental efforts to synthesize this material.