Computational investigation of half-metallicity in [formula omitted] half-Heusler alloys GeKZ (Z = Ca, Sr) using first-principles calculations

Abstract

This paper is based on the study of structural, electronic, magnetic, elastic, phonon dynamics and thermodynamic properties of d0 half-Heusler alloys GeKZ (Z = Ca, Sr) using the Density Functional Theory (DFT) approach. The investigation is carried out using the spin-polarized calculations with pseudopotential approach using Generalized Gradient Approximation by Perdew–Burke–Ernzerhof (GGA-PBE). Both the compounds GeKCa and GeKSr are found to be structurally stable in the ferromagnetic α-phase. The electronic properties in the form of spin-polarized band-structures and density of states of the compounds GeKCa and GeKSr show that they are half-metallic in nature with a finite and large half-metallic band-gap of 0.37 eV and 0.29 eV respectively in the spin-up states and a metallic behavior in the spin-down states with 100 % spin-polarization at the Fermi-level. Integral magnetic moment of 1.00 μB is obtained for both the compounds which is in accordance with the Slater–Pauling Rule for half-Heusler alloys. The elastic properties show that the compounds are mechanically stable following Born stability criteria for cubic compounds and are found to be ductile in nature. The compounds have also been found to be dynamically stable against lattice vibrations on the basis of phonon dispersion calculations. They have also been explored regarding their thermodynamic properties using the quasi-harmonic approximation. They are also examined for the preservation of the integral magnetic moment against the lattice compression and expansion. The observed properties points towards the suitability of these compounds in the spintronics applications.