Electronic, magnetic and thermal properties of Co2CrxFe1−xX (X=Al, Si) Heusler alloys: First-principles calculations

• We present electronic, magnetic and thermal properties of Co2CrxFe1−xX (X=Al, Si) Heusler alloys.
• The calculated phase diagram indicates a significant phase miscibility gap.
• The computed band structures of ternary compounds using GGA, EVGGA and mBJ schemes indicate an indirect band gap (Γ-X) for the ternary compounds Co2FeAl, Co2CrAl, Co2FeSi and Co2CrSi while both alloys have a direct band gap.
• The quasi-harmonic Debye model is successfully applied to determine the thermal properties.

Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co2CrxFe1−xX (X=Al, Si) full Heusler alloys, with L21 structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel–Vosko generalized gradient approximation (EVGGA) and modified Becke–Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co2CrxFe1−xX that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions.