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

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 μ_B, which satisfies the Slater-Pauling rule M_t = Z_t-16. The main contribution to the total magnetic moment comes from the Cr atoms (about 3.9 μ_B). Furthermore, the Curie temperature T_C 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.