Abstract
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.
Highlights
Ferromagnetic diluted magnetic semiconductors (DMS’s) have opened a way for the manipulation of the spin degree of freedom of electrons through interaction between the local moments of doped magnetic ions and the spins of charge carriers in the host semiconductors
The Zn1−xCrxTe thin films showed ferromagnetism at room temperature and their magnetic circular dichroism (MCD) signals observed at the absorption edge of ZnTe showed magnetic-field (H) and temperature (T ) dependences which follow these of magnetization (M), indicating that there is strong interaction between the spins of host s,p-band electrons and the magnetic moments of the doped Cr ions [16, 17]
x-ray magnetic circular dichroism (XMCD) intensity increases with increasing x. Both the x-ray absorption spectroscopy (XAS) and XMCD spectra are similar to those of a x = 0.45 sample previously reported [39]. These results suggest that there may be two or more kinds of Cr ions having different electronic structures as observed by XAS, the ferromagnetic properties of these films reflected on the XMCD spectra are originated from a common magnetically active component
Summary
Ferromagnetic diluted magnetic semiconductors (DMS’s) have opened a way for the manipulation of the spin degree of freedom of electrons through interaction between the local moments of doped magnetic ions and the spins of charge carriers in the host semiconductors. The Zn1−xCrxTe thin films showed ferromagnetism at room temperature and their MCD signals observed at the absorption edge of ZnTe showed magnetic-field (H) and temperature (T ) dependences which follow these of magnetization (M), indicating that there is strong interaction between the spins of host s,p-band electrons and the magnetic moments of the doped Cr ions [16, 17].
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