Constituents of magnetic anisotropy and a screening of spin-orbit coupling in solids

TL;DR

This paper uses quantum perturbation theory to analyze magnetic anisotropy and spin-orbit coupling in solids, validating results with density functional calculations and explaining microscopic origins of high anisotropy in certain magnets.

Contribution

It introduces a perturbation theory framework for analyzing magnetic anisotropy and spin-orbit effects, validated against density functional results and applied to various magnetic materials.

Findings

Perturbation theory accurately predicts magnetic anisotropy energies.

High anisotropy in FePt and CoPt is explained microscopically.

Relativistic energy calculations align with density functional results.

Abstract

Using quantum mechanical perturbation theory (PT) we analyze how the energy of perturbation of different orders is renormalized in solids. We test the validity of PT analysis by considering a specific case of spin-orbit coupling as a perturbation. We further compare the relativistic energy and the magnetic anisotropy from the PT approach with direct density functional calculations in FePt, CoPt, FePd, MnAl, MnGa, FeNi, and tetragonally strained FeCo. In addition using decomposition of anisotropy into contributions from individual sites and different spin components we explain the microscopic origin of high anisotropy in FePt and CoPt magnets.