Fe contribution to the magnetic anisotropy of $L{1_0}$-ordered FePt thin films studied by angle-dependent x-ray magnetic circular dichroism

TL;DR

This study investigates the microscopic origin of strong perpendicular magnetic anisotropy in $L1_0$-ordered FePt thin films, revealing the dominant role of Pt rather than Fe in governing the anisotropy.

Contribution

The paper provides experimental evidence that Fe $3d$ electrons' anisotropic distribution reduces PMA, highlighting the significant influence of Pt in the magnetic anisotropy of FePt films.

Findings

Finite magnetic dipole moment $m_T$ indicates out-of-plane distribution of Fe $3d$ electrons.

Fe $3d$ electron anisotropy reduces PMA, contrary to expectations.

Pt's contribution is the primary factor in the strong PMA of FePt films.

Abstract

Among magnetic thin films with perpendicular magnetic anisotropy (PMA), $L1_0$-ordered FePt has attracted significant attention because of its exceptionally strong PMA. However, the microscopic origin of its strong PMA has not been elucidated experimentally. We have investigated the contribution of the Fe $3d$ electrons to its magnetic anisotropy energy by angle-dependent x-ray magnetic circular dichroism at the Fe $L_{2,3}$ edge. By this technique, one can deduce the magnetic dipole moment $m_\text{T}$, which represents the anisotropic spatial distribution of spin-polarized electrons, and the orbital moment anisotropy (OMA) of Fe $3d$ electrons. Detected finite $m_\text{T}$ indicates that the spin-polarized Fe $3d$ electrons are distributed preferentially in the out-of-plane direction of the films. This $m_\text{T}$ of Fe overwhelms the positive contribution of OMA to PMA, and reduces the PMA of $L1_0$-ordered FePt thin films, consistent with a previous first-principles calculation. The present result implies that a large positive contribution of the non-magnetic element Pt rather than Fe governs the PMA of $L1_0$-ordered FePt thin films.