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

TL;DR

This study investigates how co-doping with donor and acceptor impurities affects the magnetic properties of Zn$_{1-x}$Cr$_x$Te, revealing changes in chromium valence states and ferromagnetic behavior through XAS and XMCD analyses.

Contribution

It provides new insights into the role of nitrogen doping and impurity co-doping on the electronic and magnetic states of Zn$_{1-x}$Cr$_x$Te, highlighting the coexistence of Cr$^{2+}$ and Cr$^{3+}$ in heavily N-doped samples.

Findings

Cr ions are divalent in undoped, I-doped, and lightly N-doped samples.

Heavily N-doped samples show coexistence of Cr$^{2+}$ and Cr$^{3+}$.

Ferromagnetism is suppressed in heavily N-doped samples.

Abstract

We have performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies of the diluted ferromagnetic semiconductor Zn$_{1-\textit{x}}$Cr$_\textit{x}$Te doped with iodine (I) or nitrogen (N), corresponding to electron or hole doping, respectively. From the shape of the Cr $2p$ absorption peak in the XAS spectra, it was concluded that Cr ions in the undoped, I-doped and lightly N-doped samples are divalent (Cr$^{2+}$), while Cr$^{2+}$ and trivalent (Cr$^{3+}$) coexist in the heavily N-doped sample. This result indicates that the doped nitrogen atoms act as acceptors but that doped holes are located on the Cr ions. In the magnetic-field dependence of the XMCD signal at the Cr $2p$ absorption edge, ferromagnetic behaviors 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.