Wrinkle formation and its effect on the magnetic properties of Cr₂Ge₂Te₆/NiO heterostructures

Increasing the ferromagnetic transition temperature in 2D ferromagnetic insulators is an important challenge for technological applications. Recently, we have reported an enhanced magnetism in Cr₂Ge₂Te₆/NiO heterostructures. The enhanced magnetism manifested in significantly increased Curie temperature and coercive field, suggesting a strongly enhanced perpendicular magnetic anisotropy. At the time, the microscopic mechanism of this enhanced magnetism remained elusive [1]. Here, we further study the possible cause of the enhancement. We performed magneto optic Kerr effect and Raman microscopy measurements on thin Cr₂Ge₂Te₆ (CGT) flakes covered by NiO. We found a correlation between the enhanced magnetism with the presence of wrinkles in the heterostructure and the Raman spectrum of the heterostructure showed CGT’s characteristic peaks shifting when probed on and around the wrinkles. Moreover, the Raman peak shift and the enhanced magnetism are more pronounced for positions closer to the wrinkles, which suggests that wrinkle-induced-strain in CGT is a possible origin of the strongly enhanced magnetism.

[1] H. Idzuchi, A.E. Llacsahuanga, X.C. Pan, K. Tanigaki, and Y.P. Chen, Appl. Phys. Lett. 115, 232403 (2019)