Ab initio Calculations of the Magnetocrystalline Anisotropy in $UAuSb_2$ Ferromagnet

The paper presents results of ab initio calculations of the magnetocrystalline anisotropy of $UAuSb_2$, a strongly anisotropic ferromagnet below 36 K. The total energy of the unit cell of $UAuSb_2$ was calculated by two methods: the full potential linear muffin-tin orbitals method and by the full-potential local-orbital minimum basis band structure code. The computations were done for the following quantization directions in the tetragonal unit cell (orientations of the magnetization vector M): [010], [001], [011], [110], [111], and [11½] . The anisotropic contribution to the total energy for various directions were fitted by the least-squares procedure to the expression for the magnetocrystalline energy suitable for tetragonal symmetry $E_A=K(α_x^4 +α_y^4)+ K_2α_z^2$, where $(α_x,α_y,α_z)$ is a unit vector along the direction of magnetization M. The band structure calculations predict the direction [111] as the easy axis of magnetization. Values of the calculated anisotropy constants at T=0 are provided.