Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn1-xCrxTe

The electronic structure of the Cr ions in the diluted ferromagnetic semiconductor Zn1-xCrxTe ( x = 0.03 and 0.15) thin films has been investigated using x-ray magnetic circular dichroism (XMCD) and photoemission spectroscopy (PES). Magnetic-field (H) and temperature (T) dependences of the Cr 2p XMCD spectra correspond well to the magnetization measured by a SQUID magnetometer. The line shape of the Cr 2p XMCD spectra is independent of H, T and x, indicating that the ferromagnetism originated from the same electronic states of the Cr ion. A cluster-model analysis indicates that although there are two or more kinds of Cr ions in the Zn1-xCrxTe samples, the ferromagnetic XMCD signal originated from Cr ions substituted for the Zn site. The Cr 3d partial density of states extracted using Cr 2p -> 3d resonant PES shows a broad feature near the top of the valence band, suggesting strong s,p-d hybridization. No density of states is detected at the Fermi level, consistent with their insulating behavior. Based on these findings, we conclude that the double-exchange mechanism cannot explain the ferromagnetism in Zn1-xCrxTe.