Contributions of Co and Fe orbitals to Perpendicular Magnetic Anisotropy of MgO/CoFeB Bilayers with Spin-Orbit-Torque-Related (Ta, W, IrMn, and Ti) Underlayers

TL;DR

This study investigates how different underlayer materials influence the perpendicular magnetic anisotropy in CoFeB/MgO bilayers, revealing orbital moment suppression effects related to interfacial intermixing and material choice.

Contribution

It provides new insights into the orbital contributions of Co and Fe to PMA in bilayers with various spin-orbit-torque-related underlayers.

Findings

Interfacial intermixing suppresses Fe's perpendicular orbital moment.

Intermixing suppresses both perpendicular and in-plane orbital moments of Co.

Different underlayers affect the saturation magnetization and PMA strength.

Abstract

We study the perpendicular magnetic anisotropy (PMA) of the CoFeB/MgO bilayers in contact with W, Ta, IrMn and Ti which has been suggested as the spin-orbit-torque-related underlayers. The saturation magnetization of the CoFeB depends on the underlayer materials due to formation of a dead-layer, affecting PMA strength of each film. The x-ray magnetic circular dichroism measurement reveals that the interfacial intermixing suppresses only the perpendicular orbital moment of Fe, while the intermixing simultaneously suppresses both the perpendicular and in-plane orbital moments of Co.