First-principles search for half-metallic ferromagnetism in CsCrZ2 (Z = O, S, Se or Te) Heusler alloys

Abstract

Exploring highly spin-polarized materials is crucial for the development of spin-based devices. In this paper, we investigate the atomic structure, electronic, half-metallic and magnetic properties of the CsCrZ2 (Z = O, S, Se or Te) Heusler alloys, by performing first-principles calculations based on density functional theory (DFT). The geometry optimization process shows that the alloys are more stable in Cu2MnAl type structure than in Hg2CuTi one. To find a magnetic ground state, the total energy of the alloys is calculated in the non-magnetic (NM), ferromagnetic (FM) and anti-ferromagnetic (AFM) ordering. We find that, the FM ordering yields the lowest energy, thereby confirming that the alloys are FM in the ground state. On computing the cohesive and formation energy in the ground state, it is found that alloys are chemically and thermodynamically stable, respectively. Spin polarized band structures and density of states (DOS) demonstrate that the CsCrO2, CsCrS2 and CsCrSe2 alloys are true half-metals with 100% spin-polarization at the Fermi level, while the CsCrTe2 alloy is predicted as highly spin polarized material. Furthermore, the CsCrO2, CsCrS2 and CsCrSe2 alloys possess 2.529, 2.250 and 2.050 eV gaps in the spin down band structure, respectively. The calculated total magnetic moments reveal that half-metallic alloys have an integral total magnetic moment of 3.000 μB, which satisfies the Slater-Pauling rule Mt = Zt-16. The main contribution to the total magnetic moment comes from the Cr atoms (about 3.9 μB). Furthermore, the Curie temperature TC calculated within classical Heisenberg model is estimated to be about 822 K (CsCrO2), 685 K (CsCrS2), 753 K (CsCrSe2) and 636 K (CsCrTe2). The obtained high spin polarization and above room temperature FM ordering make the materials as promising materials to be used in spintronic technology.