# CoFeB/MgO/CoFeB structures with orthogonal easy axes: perpendicular anisotropy and damping

## TL;DR

This study investigates the magnetic properties, damping, and anisotropy of CoFeB/MgO/CoFeB structures with orthogonal easy axes, revealing nonlinear relationships between effective magnetization and g-factor asymmetry, and effects of annealing on magnetic alignment.

## Contribution

It provides new insights into the magnetic anisotropy and damping behavior of orthogonal easy axis structures, including the impact of annealing on magnetic alignment.

## Key findings

- Orthogonal easy axes with specific magnetization values for top and bottom layers.
- Nonlinear dependence of effective magnetization on g-factor asymmetry.
- Annealing induces collinear perpendicular easy axes but increases linewidth due to inhomogeneous broadening.

## Abstract

We report on the Gilbert damping parameter $\alpha$, the effective magnetization $4\pi M_{eff}$, and the asymmetry of the $g$-factor in bottom-CoFeB(0.93~nm)/MgO(0.90--1.25~nm)/CoFeB(1.31~nm)-top as-deposited systems. Magnetization of CoFeB layers exhibits a specific noncollinear configuration with orthogonal easy axes and with $4\pi M_{eff}$ values of $+2.2$ kG and $-2.3$ kG for the bottom and top layers, respectively. We show that $4\pi M_{eff}$ depends on the asymmetry $g_\perp - g_\parallel$ of the $g$-factor measured in the perpendicular and the in-plane directions revealing a highly nonlinear relationship. In contrast, the Gilbert damping is practically the same for both layers. Annealing of the films results in collinear easy axes perpendicular to the plane for both layers. However, the linewidth is strongly increased due to enhanced inhomogeneous broadening.