First-Principles Calculations of the Magnetocrystalline Anisotropy Energy in Disordered Alloys Using Wannier-based Coherent Potential Approximation

Abstract

We present a method for calculating the magnetocrystalline anisotropy energy (MAE) of disordered alloys using Green’s functions constructed from Wannier Hamiltonians within the coherent potential approximation (Wannier-CPA). The MAE of a disordered alloy system is obtained from the difference in thermodynamic potential between two magnetization directions, with the potential evaluated using the Luttinger–Ward functional. For validation, the MAE of Fe x Ni 1− x and Fe x Pd 1− x is calculated using both the Wannier-CPA method and the Korringa–Kohn–Rostoker (KKR) method combined with the CPA. The results obtained by Wannier-CPA are in good agreement with those from KKR-CPA, reproducing the composition dependence of the MAE and the characteristic behavior specific to each system. Furthermore, analysis of the in-plane MAE of Fe x Pd 1− x shows that it changes sign near x [Formula: see text] 0.425. This approach provides a route to evaluate the MAE of disordered alloys using Wannier Hamiltonians generated from various first-principles codes, while retaining the efficiency of Wannier interpolation.