Effects of pressure on the magnetic anisotropy of ferromagnetic insulator Cr$_{\mathrm{2}}$Ge$_{\mathrm{2}}$Te$_{\mathrm{6}}$

Cr$_{\mathrm{2}}$Ge$_{\mathrm{2}}$Te$_{\mathrm{6}}$ is an interesting atomically layered ferromagnetic insulator with space group $R\overline 3 $ that has a Curie temperature of \textasciitilde 61 K and a band gap of \textasciitilde 0.2 eV. Owing to the van der Waals nature of the crystal structure, both electronic and magnetic properties depends on the interlayer coupling; therefore, it is interesting to study the effects of the interlayer spacing on physical properties. In this study, we apply a hydrostatic pressure to a CGT crystal up to 2000 PSI while measuring its magneto-transport properties with an external magnetic field applied along the c-axis of CGT. With increasing pressure, we observe a systematic increase in the anisotropic magnetoresistance ratio accompanied by a decrease in the band gap. In the meantime, the saturation field in the magnetoresistance increases as the pressure increases, indicating that the magnetization gradually favors to be in the ab-plane. This induced anisotropy change could be attributed to the increased interlayer coupling as the layers are bought closer to each other.