Nanomechanical probing and strain tuning of the Curie temperature in suspended Cr$_2$Ge$_2$Te$_6$ heterostructures

TL;DR

This study investigates how mechanical strain influences the magnetic transition temperature in suspended 2D Cr$_2$Ge$_2$Te$_6$ heterostructures, revealing magneto-elastic coupling and strain-induced Curie temperature enhancement.

Contribution

It demonstrates the first direct measurement of strain-tuning of the Curie temperature in suspended 2D magnetic heterostructures using nanomechanical resonators.

Findings

Magneto-elastic coupling affects resonance frequency near T_C.

Strain compensation in heterostructures allows precise T_C probing.

Electrostatically induced strain enhances T_C by approximately 2.5 K.

Abstract

Two-dimensional (2D) magnetic materials with strong magnetostriction are interesting systems for strain-tuning the magnetization, enabling potential for realizing spintronic and nanomagnetic devices. Realizing this potential requires understanding of the magneto-mechanical coupling in the 2D limit. In this work, we suspend thin Cr$_2$Ge$_2$Te$_6$ layers, creating nanomechanical membrane resonators. We probe its mechanical and magnetic properties as a function of temperature and strain. Pronounced signatures of magneto-elastic coupling are observed in the temperature-dependent resonance frequency of these membranes near $T_{\rm C}$. We further utilize Cr$_2$Ge$_2$Te$_6$ in heterostructures with thin layers of WSe$_2$ and FePS$_3$, which have positive thermal expansion coefficients, to compensate the negative thermal expansion coefficient of Cr$_2$Ge$_2$Te$_6$ and quantitatively probe the corresponding $T_{\rm C}$. Finally, we induce a strain of $0.016\%$ in a suspended heterostructure via electrostatic force and demonstrate a resulting enhancement of $T_{\rm C}$ by $2.5 \pm 0.6$ K in the absence of an external magnetic field.