Enhanced Room Temperature Ferromagnetism in Highly Strained 2D Semiconductor Cr₂Ge₂Te₆

Abstract

Emergent magnetism in van der Waals materials offers exciting opportunities in fabricating atomically thin spintronic devices. One pertinent obstacle has been the low transition temperatures (<i>T</i>_c) inherent to these materials, precluding room temperature applications. Here, we show that large structural gradients found in highly strained nanoscale wrinkles in Cr₂Ge₂Te₆ (CGT) lead to significant increases of <i>T</i>_c. Magnetic force microscopy was utilized in characterizing multiple strained CGT nanostructures leading to experimental evidence of elevated <i>T</i>_c, depending on the strain percentage estimated from finite element analysis. Our findings are further supported by <i>ab initio</i> and DFT studies of the strained material, which indicates that strain directly augments the ferromagnetic coupling between Cr atoms in CGT, influenced by superexchange interaction; this provides strong insight into the mechanism of the enhanced magnetism and <i>T</i>_c.