Effect of co-doping of donor and acceptor impurities in the ferromagnetic semiconductor Zn1-xCrxTe studied by soft x-ray magnetic circular dichroism

摘要

We have performed x-ray absorption spectroscopy (XAS) and x-ray magneticcircular dichroism (XMCD) studies of the diluted ferromagnetic semiconductorZn$_{1-\textit{x}}$Cr$_\textit{x}$Te doped with iodine (I) or nitrogen (N),corresponding to electron or hole doping, respectively. From the shape of theCr $2p$ absorption peak in the XAS spectra, it was concluded that Cr ions inthe undoped, I-doped and lightly N-doped samples are divalent (Cr$^{2+}$),while Cr$^{2+}$ and trivalent (Cr$^{3+}$) coexist in the heavily N-dopedsample. This result indicates that the doped nitrogen atoms act as acceptorsbut that doped holes are located on the Cr ions. In the magnetic-fielddependence of the XMCD signal at the Cr $2p$ absorption edge, ferromagneticbehaviors were observed in the undoped, I-doped, and lightly N-doped samples,while ferromagnetism was considerably suppressed in heavily N-doped sample,which is consistent with the results of magnetization measurements.