Electronic structures, magnetic properties and strain effects of quaternary Heusler alloys FeMnCrZ (Z = P, As, Sb, Bi, Se, Te)

We have systematically investigated the electronic structures, magnetic properties and strain effects of quaternary Heusler compounds FeMnCrZ (Z = P, As, Sb, Bi, Se, Te) by using the self-consistent full-potential linearized-augmented plane-wave (FPLAPW) method with the generalized gradient approximation (GGA) and the local density approximation (LDA) + U methods based on the density functional theory (DFT). By analyzing the electronic structures of these six compounds within GGA, we have found that the FeMnCrAs, FeMnCrSb, and FeMnCrTe alloys show excellent half-metallic ferrimagnetism, and the FeMnCrP and FeMnCrBi compounds present near half-metallicity. By using the LDA + U method, we found that FeMnCrP, FeMnCrAs and FeMnCrTe are half-metals. The total spin magnetic moments for all the half-metals satisfy the Slater-Pauling 24 electron-rule, confirming the existence of the half-metallic gap. The estimated Curie temperatures of all compounds exceed the room temperature, making the half-metal compounds promising for spintronic applications. Finally, the effects of uniform and tetragonal strain have been investigated. The half-metallicity can be either enhanced, reduced or destroyed by a uniform strain. A ferrimagnetism to ferromagnetism phase transition can be induced by a uniform lattice expansion within the LDA + U method. The effects of the tetragonal distortion turn out to be negligible for these compounds.