First-principles study of magnetic disordering and alloying effects on phase stability and elastic constants ofCo2CrZ (Z = Ga, Si, Ge) alloys

Using the exact Muffin-Tin orbital method combined with the coherent potential approximation, the effectsof magnetic disordering and alloying effects on the phase stability of L21- and D022-Co2CrZ (Z = Ga, Si, Ge)alloys are systematically investigated at 0 K in the present work. It is shown that at 0 K, the lattice parameter,bulk modulus, magnetic moments, and elastic constants of the studied L21 alloys are in line with the availabletheoretical and experimental data. In the ferromagnetic state, these alloys possess L21 structure; with themagnetic disordering degree (y) increasing, the energy of the phase increases relatively and finally turns fromlower than D022 phase to higher than D022 phase. As a result, when y >= 0.1 (0.2), then Z = Si and Ge (Z =Ga) alloys are stabilized by the D022 phase. With y increasing, the tetragonal shear elastic modulus (C' =(C11-C12)/2) also turns soft, indicating that the magnetic disorderingis conducive to the lattice tetragonaldeformation in the three alloys from both the energetic view and the mechanical view. The electronicorigination of the magnetic disordering effect on the stabilities of the L21 and D022 phases can be ascribed to theJahn-Teller instability effect. In the FM L21-Co2CrGa1-xSix and L21-Co2CrGa1-xGex quaternary alloys, with xincreasing, the total magnetic moment increases monotonically according to the Slater-Pauling rule, and C' alsostiffens, reflecting that the adding of Si and Ge can promote the mechanical stability of L21-Co2CrGa alloy,thereby depressing the lattice tetragonal deformation

Automated summary

Using the exact Muffin-Tin orbital method combined with the coherent potential approximation, the effect of magnetic disordering and alloying effects on the phase stability of L21- and D022-Co2CrZ (Z = Ga, Si, Ge) alloys are systematically investigated at 0 K. It is found that magnetic disordering has a significant impact on the stability of phases, and the addition of Si and Ge can promote the mechanical stability of L21-Co2CrGa alloy.