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 (T 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 T c. Magnetic force microscopy was utilized in characterizing multiple strained CGT nanostructures leading to experimental evidence of elevated T c, depending on the strain percentage estimated from finite element analysis. Our findings are further supported by ab initio 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 T c.

Nano-Patterned Magnetic Edges in CrGeTe3 for Quasi 1-D Spintronic Devices

“…Strain should also be considered as one of the mechanisms to induce edge magnetization. It was shown that strain can enhance magnetism in CGT. , It is plausible that some strain appears at low temperatures at the interface between the amorphous and crystalline CGT regions. The last mechanism that we can consider is related to the in-plane dangling bond.…”

Ferroic Phases in Two-Dimensional Materials

“…192 Notably, Adam O'Neill et al experimentally detected the strain-induced increment of T C in Cr 2 Ge 2 Te 6 utilizing MFM combined with the ab initio and DFT studies (Figure 21e,f). 175 The wrinkles were created by mechanically bending a flexible substrate coated with Cr 2 Ge 2 Te 6 (Figure 21g). It was calculated that the T C of 1L Cr 2 Ge 2 Te 6 could elevate from ∼50 K to ∼150 K with 5% strain, while the T C of the bilayer could increase close to room temperature with 5% strain (Figure 21f).…”

“…2D ferromagnets coupled with their electronic and optical properties, could facilitate advanced magnetic, ,, magnetoelectric, − and magneto–optical − applications. Flexibility and facile modulation of ferromagnetic/antiferromagnetic properties by local or external perturbations, such as strain, − interlayer interactions, − and electric field modulation, − are well-known advantages of 2D ferromagnets.…”

“…(g) The 3D MFM phase image of strained CGT showing the strain induced room-temperature magnetism. Reproduced with permission from ref . Copyright 2023 American Chemical Society.…”

“…According to the superexchange interactions, the calculation result implies that tensile strain triggers a higher energy difference between the 3d orbitals of Cr and the 4p orbitals of Se . Notably, Adam O’Neill et al experimentally detected the strain-induced increment of T C in Cr 2 Ge 2 Te 6 utilizing MFM combined with the ab initio and DFT studies (Figure e,f) . The wrinkles were created by mechanically bending a flexible substrate coated with Cr 2 Ge 2 Te 6 (Figure g).…”