Mechanism of uniaxial magnetocrystalline anisotropy in transition metal alloys

TL;DR

This study uses first-principles calculations to analyze the mechanisms behind uniaxial magnetocrystalline anisotropy in various transition metal alloys, revealing how electronic structure and spin-orbit interactions influence anisotropy energy.

Contribution

It systematically elucidates the specific mechanisms of uniaxial magnetocrystalline anisotropy in transition metal alloys using first-principles methods, highlighting conditions for increasing anisotropy energy.

Findings

Large anisotropy in FePt and CoPt due to strong Pt spin-orbit interaction.

Comparable anisotropy energies in MnAl, MnGa, and FeCo despite weak spin-orbit interactions.

Electronic structure influences anisotropy through spin-orbit interaction selection rules.

Abstract

Magnetocrystalline anisotropy in transition metal alloys (FePt, CoPt, FePd, MnAl, MnGa, and FeCo) was studied using first-principles calculations to elucidate its specific mechanism. The tight-binding linear muffin-tin orbital method in the local spin-density approximation was employed to calculate the electronic structure of each compound, and the anisotropy energy was evaluated using the magnetic force theorem and the second-order perturbation theory in terms of spin-orbit interactions. We systematically describe the mechanism of uniaxial magnetocrystalline anisotropy in real materials and present the conditions under which the anisotropy energy can be increased. The large magnetocrystalline anisotropy energy in FePt and CoPt arises from the strong spin-orbit interaction of Pt. In contrast, even though the spin-orbit interaction in MnAl, MnGa, and FeCo is weak, the anisotropy energies of these compounds are comparable to that of FePd. We found that MnAl, MnGa, and FeCo have an electronic structure that is efficient in inducing the magnetocrystalline anisotropy in terms of the selection rule of spin-orbit interaction.