Magnetocrystalline anisotropy calculation of Fe-Ga alloys by the magnetic torque method

The magnetic properties of body-centered cubic structures of Fe$_{100-x}$Ga$_x$ were investigated using the density functional theory. The dependence of the magnetocrystalline anisotropy (MCA) energy as a function of the tetragonal distortions was obtained by the help of the magnetic torque method implemented in the SPR-KKR software package. The dependence of MCA energy on the strain is linear and has a positive slope for a disordered A2 phase and a partially ordered B2 one. For ordered D0$_3$ structure, this dependence demonstrates a complex nonlinear behavior. The B2 phase makes the main contribution to tetragonal magnetostriction in the region of concentrations $21 \leq x \leq 25$ at.%. The shear modulus obtained using the SPR-KKR software package decreases with increasing Ga concentration.