Investigation of Half-Metallic, Magnetic, and Thermodynamic Properties of Quaternary Half-Heusler NiCoFeX(X=S,As and Ge) using First-Principle Calculations
Abstract
The First Principle Density Functional Theory (DFT) method was used to investigate the half-metallic character, magnetic and thermodynamic properties of NiCoFeX(X=Si,As and Ge). Electronic and magnetic properties such as band structures,densities of states, and magnetic moments, spin – polarization indices of each alloy are also determined to confirm half-metallicity and ferromagnetism. Thermodynamic properties such as Free Energy, Entropy,Heat Capacity and Debye Temperature are also computed using Quantum Espresso-based Thermo_pw code. The half-metallic band gaps of NiCoFeAs, NiCoFeSi and NiCoFeGe are 0.206eV, 0.205eV and 0.203eV respectively.The spin-up channels in the electronic band structures of NiCoFeX(X=Si,As and Ge) have indirect energy band gap,indicating that they exhibit half-metallic character .The quaternary Heuslers NiCoFeX(X=Si,As and Ge) are accurately ferromagnetic as they all obey Slater Paulin’s rule having magnetic moments of 4.0215μB,4.1573μB and 4.6711μB respectively and are 100% spin-polarized.The Curie Temperatures Tc of NiCoFeX(X=Si,As and Ge) are 827K,3631K and 827K respectively ( above the room temperature of 300K). However, only NiCoFeAs, and NiCoFeGe preserved their ferromagnetism after undergoing strain field. This makes them preferable candidates in the field of semiconductor physics. The heat capacities of NiCoFeX(X=Si,As and Ge) obey Dulong-petit law showing that they have good thermal applications in optoelectronic devices e.g. magnetic tunnel Junctions (MTJs),giant magneto-resistance devices (GMRs),Photo diodes, Solar cells etc.
