Spin-split valence bands of the ferromagnetic insulator Cr2Ge2Te6 studied by angle-resolved photoemission spectroscopy

The low-energy electronic structure of a ferromagnetic insulator Cr2Ge2Te6 was studied by angle-resolved photoemission spectroscopy (ARPES). A broadening of the ARPES spectra, which we ascribe to a splitting of the valence band, has been observed at low temperature. Through temperature dependent measurements, we found that the band splitting presented a transition at similar to 60-70 K, which is consistent with the ferromagnetic transition temperature of Cr2Ge2Te6. Therefore, we suggested that the splitting of the valence band is due to the spin polarization effect of Te 5p states by Cr 3d states, which is compatible with the superexchange coupling through Cr-Te-Cr to form long-range ferromagnetic order in Cr2Ge2Te6.