Magnetocrystalline anisotropy of FePt: a detailed view

TL;DR

This paper investigates the magnetocrystalline anisotropy of FePt using ab-initio methods, revealing the importance of many-body effects and analyzing the underlying mechanisms of MCA.

Contribution

It provides a detailed ab-initio analysis of FePt's MCA, highlighting the role of many-body effects and the limitations of second order perturbation theory.

Findings

MCA energies from different methods agree well

Calculated MCA significantly differs from experimental values

Main MCA mechanism can be described by second order perturbation theory

Abstract

To get a reliable ab-initio value for the magneto-crystalline anisotropy (MCA) energy of FePt, we employ the full-potential linearized augmented plane wave (FLAPW) method and the full-potential Korringa-Kohn-Rostoker (KKR) Green function method. The MCA energies calculated by both methods are in a good agreement with each other. As the calculated MCA energy significantly differs from experiment, it is clear that many-body effects beyond the local density approximation are essential. It is not really important whether relativistic effects for FePt are accounted for by solving the full Dirac equation or whether the spin-orbit coupling (SOC) is treated as a correction to the scalar-relativistic Hamiltonian. From the analysis of the dependence of the MCA energy on the magnetization angle and on the SOC strength it follows that the main mechanism of MCA in FePt can be described within second order perturbation theory. However, a distinct contribution not accountable for by second order perturbation theory is present as well.