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

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