Cr doping-induced ferromagnetism in the spin-glass Cd1-xMnxTe studied by x-ray magnetic circular dichroism

TL;DR

This study reveals that doping Cd1-xMnxTe with Cr induces ferromagnetism through ferromagnetic coupling between Cr and Mn ions, as shown by element-specific magnetic measurements.

Contribution

It provides direct experimental evidence of ferromagnetic interaction between Cr and Mn ions in Cd1-xMnxTe using XAS and XMCD techniques.

Findings

Cr and Mn are divalent in the doped material

Ferromagnetic components of Cr and Mn are aligned

Mn magnetization increases with Cr doping

Abstract

The prototypical diluted magnetic semiconductor Cd1-xMnxTe is a spin glass (x<0.6) or an antiferromagnet (x>0.6), but becomes ferromagnetic upon doping with a small amount of Cr atoms substituting for Mn. In order to investigate the origin of the ferromagnetism in Cd1-x-yMnxCryTe, we have studied its element specific magnetic properties by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) at the Cr and Mn L2,3 edges. Thin films were grown by molecular beam epitaxy with a fixed Mn content of x = 0.2 and varying Cr content in the range of y = 0 - 0.04. Measured XAS and XMCD spectra indicate that both Cr and Mn atoms are divalent and that the ferromagnetic or superparamagnetic components of Cr and Mn are aligned in the same directions. The magnetization of Mn increases with increasing Cr content. These results can be explained if ferromagnetic interaction exists between neighboring Mn and Cr ions although interaction between Mn atoms is largely antiferromagnetic. We conclude that each ferromagnetic or superparamagnetic cluster consists of ferromagnetically coupled several Cr and a much larger number of Mn ions.