Strong effects of uniaxial pressure and short-range correlations in Cr2Ge2Te6

Cr${}_2$Ge${}_2$Te${}_6$ is a quasi-2D semiconducting van der Waals ferromagnet down to the bilayer with great potential for technological applications. Engineering the critical temperature to achieve room temperature applications is one of the critical next steps on this path. Here, we report high-resolution capacitance dilatometry studies on Cr${}_2$Ge${}_2$Te${}_6$ single crystals which directly prove significant magnetoelastic coupling and provide quantitative values of the large uniaxial pressure effects on long-range magnetic order ($\mathrm{\partial }{T}_{\mathrm{C}}\mathrm{/}\mathrm{\partial }{p}_{\mathrm{c}}$ = 24.7 K/GPa and $\mathrm{\partial }{T}_{\mathrm{C}}\mathrm{/}\mathrm{\partial }{p}_{\mathrm{a}\mathrm{b}}$ = $-$15.6 K/GPa) derived from thermodynamic relations. Moderate in-plane strain is thus sufficient to strongly enhance ferromagnetism in Cr${}_2$Ge${}_2$Te${}_6$ up to room temperature. Moreover, unambiguous signs for short-range magnetic order up to 200~K are found.