Perpendicularly magnetized Tb/Co multilayers featuring tilted uniaxial anisotropy: Experiments and modeling

TL;DR

This study investigates the magnetic properties of Tb/Co multilayers, revealing how their compensation temperature varies with Tb thickness and proposing a model to explain the tilted anisotropy affecting their magnetic behavior.

Contribution

The paper provides a systematic experimental analysis of Tb/Co multilayers and introduces a model explaining tilted uniaxial anisotropy and its effects on magnetic properties.

Findings

Compensation temperature varies linearly with Tb thickness.

Estimated uniaxial anisotropy constant is approximately 330 kJ/m$^3$.

Tilted anisotropy explains hysteresis in in-plane loops.

Abstract

Rare earth/transition metal (RE/TM) multilayers with perpendicular magnetic anisotropy are key ingredients for the development of spintronic applications. Their compensation temperature depends on the ratio of the thicknesses of rare earth and transition metal, allowing their magnetic properties to be tuned with temperature while maintaining their anisotropy even in nanometer-scale devices. In this work, we performed a thorough structural characterization and systematically investigate the magnetic properties of a whole family of ferrimagnetic [Tb/Co]$_{\times 5}$ multilayers varying the Tb thickness in the range of 0.4 nm - 1.25 nm. A linear dependence of the compensation temperature on the Tb layer thickness was observed. Moreover, a uniaxial anisotropy constant of 330$\pm$30 kJ/m$^3$, which is close to the values reported by other authors, was estimated. Additionally, we proposed a model to gain a better understanding of the angular dependence of the magnetization loops and the linear dependence of the compensation temperature. We present strong evidence demonstrating that the perpendicular anisotropy must be tilted away from the perpendicular axis in order to explain the observed features, particularly the hysteresis in the in-plane loops. Our work advances the understanding of DC magnetic properties in thin RE/TM ferrimagnetic films, which has the potential to impact different fields where these materials are involved.