Pressure control of the magnetic anisotropy of the quasi-two-dimensional van der Waals ferromagnet Cr$_2$Ge$_2$Te$_6$

TL;DR

This study investigates how hydrostatic pressure affects the magnetic properties of Cr$_2$Ge$_2$Te$_6$, revealing a gradual suppression of ferromagnetism and reduction of magnetocrystalline anisotropy, with implications for strain-engineered magnetic devices.

Contribution

It provides the first detailed pressure-dependent analysis of both static magnetization and ferromagnetic resonance in Cr$_2$Ge$_2$Te$_6$, highlighting the evolution of magnetic anisotropy under pressure.

Findings

Ferromagnetic transition temperature decreases with pressure.

Magnetocrystalline anisotropy diminishes but remains positive up to 2.39 GPa.

Saturation magnetization remains constant up to 2.8 GPa.

Abstract

We report the results of the pressure-dependent measurements of the static magnetization and of the ferromagnetic resonance (FMR) of Cr$_2$Ge$_2$Te$_6$ to address the properties of the ferromagnetic phase of this quasi-two-dimensional van der Waals magnet. The static magnetic data at hydrostatic pressures up to 3.4 GPa reveal a gradual suppression of ferromagnetism in terms of a reduction of the critical transition temperature, a broadening of the transition width and an increase of the field necessary to fully saturate the magnetization $M_{\rm s}$. The value of $M_{\rm s} \simeq 3\mu_{\rm B}$/Cr remains constant within the error bars up to a pressure of 2.8 GPa. The anisotropy of the FMR signal continuously diminishes in the studied hydrostatic pressure range up to 2.39 GPa suggesting a reduction of the easy-axis type magnetocrystalline anisotropy energy (MAE). A quantitative analysis of the FMR data gives evidence that up to this pressure the MAE constant $K_{\rm U}$, although getting significantly smaller, still remains finite and positive, i.e. of the easy-axis type. Therefore, a recently discussed possibility of switching the sign of the magnetocrystalline anisotropy in Cr$_2$Ge$_2$Te$_6$ could only be expected at still higher pressures, if possible at all due to the observed weakening of the ferromagnetism under pressure. This circumstance may be of relevance for the design of strain-engineered functional heterostructures containing layers of Cr$_2$Ge$_2$Te$_6$.