DFT investigation of half-metallic ferromagnetic rare earth based spinels MgHo2Z4 (Z = S, Se)

Abstract

Half-metallic ferromagnetism, mechanical as well as thermoelectric properties for rare earth-based spinels MgHo2Z4 (Z = S, Se) were investigated using density functional theory (DFT). Structural optimization was done with Perdew-Burke-Ehrenzorf (PBE)sol-generalized gradient approximation (GGA) to calculate the lattice constant of both spinels comparable to experimental data. In addition, Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase. For ferromagnetic (FM) state stability, we also calculated the energy differences among FM, antiferromagnetic (AFM), and non-magnetic (NM) states. Additionally, Curie temperatures of ferromagnetic phases were also estimated. We used Trans-Blaha improved Becke-Johnson (TB-mBJ) potential functional for electronics as well as magnetic characteristics, which lead to the consistent explanation of half-metallic ferromagnetism, representing the whole band-occupancy in material with exact detail of density of states (DOS). The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS. Further, spin magnetic moment was explained in terms of anion, cation, and sharing charge on studied spinels. In addition, the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.