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

Abstract

Two-dimensional (2D) magnetic materials with strong magnetostriction, like Cr2Ge2Te6 (CGT), provide opportunities for tuning their magnetic state with potential applications in spintronic and magneto-mechanical devices. However, realizing this potential requires understanding their mechanical properties, such as the Young's modulus, and the ability to controllably strain the magnets and monitor their ferromagnetic Curie temperature TC on a device level. In this work, we suspend thin CGT layers to form nanomechanical membrane resonators. We then probe the mechanical and magnetic properties of CGT as a function of temperature and strain by static and dynamic nanomechanical methods. Pronounced signatures of magneto-elastic coupling are observed in the temperature-dependent resonance frequency of these membranes at the TC. We further utilize CGT in heterostructures with thin WSe2 and FePS3 layers to control the strain in CGT flakes and quantitatively probe the transition temperatures of all materials involved. In addition, an enhancement of TC by 2.5 ± 0.6 K in CGT is realized by electrostatic force straining the heterostructure of 0.016% in the absence of an external magnetic field. Nanomechanical strain thus offers a compelling degree of freedom to probe and control magnetic phase transitions in 2D layered ferromagnets and heterostructures.