Design and theoretical study of Heusler compounds based on transition metals for applications in spintronics and proper energy: Ab-initio approach with WIEN2k.

Abstract

In this thesis, we detailed the structural, elastic, thermodynamic, electronic, and magnetic proper- ties of the following alloys: Pr2RhZ, Pr2CoZ, Ir2ScZ, Rn2MnZ, and the quaternary Heusler compound CrPrCoZ, where Z = Al, Ga, In, Ge, Sb, Sn, or Te. The alloys were based on rare-earth and transition metals. The calculations were carried out within the framework of density functional theory (DFT) utilizing the full-potential linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k package. In order to optimize the structure, the GGA-PBE exchange-correlation functional was employed. This allowed precise calculation of the elastic constants, bulk moduli, equilibrium lattice parameters, and formation energies. Indicators of mechanical stability and ductility were assessed by calculating elastic moduli according to the Born–Huang criteria. The presence of half-metallic or spin-gapless behavior, bandgap characteristics, and spin polar- ization were evaluated by analyzing spin-polarized electronic band structures together with total and projected densities of states (DOS/PDOS). Magnetic configurations were examined by comparing ferromagnetic, paramagnetic, and ferrimagnetic phases. For several compounds, the calculated total and atomic magnetic moments follow the Slater–Pauling rule, indicating strongly spin-polarized and well-defined integer magnetic moments. Vibrational and thermodynamic properties were investigated using the quasi-harmonic Debye model to study heat capacities, entropies, thermal expansion coefficients, and Debye temperatures as functions of temperature and pressure. These results provide insights into lattice stability, anhar- monic effects, and phonon-mediated thermal transport relevant to thermoelectric and magnetocaloric applications. Overall, the computational results demonstrate that the investigated Heusler compounds are struc- turally stable, mechanically robust, and electronically promising. Their strong spin polarization, half- metallic character, and stable magnetic ordering make them attractive candidates for next-generation spintronic devices, magnetic sensors, and energy-efficient technologies.