Systematic, First Principle Study of Ambient Temperature Ferromagnetism and Elastic Anisotropy of Cubic Ca0.75TM0.25S (TM = Mn, Co, and Ni) Ternary Alloys: Using mBJ Functional

Abstract

Ab initio calculations are performed to investigate theoretically the structural stability, electronic, magnetic, and elastic properties of dilute magnetic semiconductors Ca0.75TM0.25S (TM = Mn, Co, and Ni). These materials crystallize in the ferromagnetic rock-salt phase and are made by doping the CaS binary semiconductor with transition metals at a fixed concentration. Calculations are performed using the full-potential linearized augmented plane wave method, plus the local orbital method (FP-LAPW+lo). The correlation exchanges potential and the structural properties are calculated using the generalized gradient approximation proposed by Perdew-Burk-Ernzerhof (PBE-GGA) and the electronic and magnetic properties are calculated using the Becke and Johnson modified local density approximation (mBJ–LDA). The comparison of curves giving energy as a function of volume in the fundamental state of the compounds in the ferromagnetic (FM), antiferromagnetic (AFM), and paramagnetic (PM) phases presented that the compounds are stable in the ferromagnetic phase. Analysis of the electronic properties showed that Ca0.75Mn0.25S, Ca0.75Co0.25S, and Ca0.75Ni0.25S are all ferromagnetic semiconductors. Various parameters like spin-exchange splittingΔx(d), crystal field energyΔECrystal, and exchange constants N0αand N0β have also confirmed a stable ferromagnetic state. The magnetic study revealed a strong contribution to the value of the total magnetic moment of the compounds, with low contributions coming from the non-magnetic atoms Ca and S. The Curie temperature values, calculated by the mean-field approximation, are 240.78 K, 228.79 K, and 150.31 K in the compounds containing Mn, Co, and Ni, respectively. The study of the mechanical properties of the host semiconductors CaS doped with transition metals, Mn, Co, and Ni, carried out at zero pressure has shown that all compounds are brittle and mechanically stable.