Element specific magnetic properties of Gd-doped GaN: Very small polarization of Ga and paramagnetism of Gd

Abstract

Element specific x-ray magnetic dichroism measurements have been carried out at the $\text{Ga}\text{ }K$ and Ga and $\text{Gd}\text{ }{L}_{3}$ edges of the dilute magnetic semiconductor (DMS) Gd:GaN grown by molecular beam epitaxy. This DMS material has previously been reported to exhibit room temperature magnetic order accompanied by colossal effective magnetic moments. We detect only a very small magnetic polarization of the order of at most ${10}^{\ensuremath{-}5}{\ensuremath{\mu}}_{B}/\text{Ga}$ atom in Gd:GaN which cannot account for the colossal effective magnetic moments. Further, the element specific magnetic properties at the Gd sites do not reveal any ferromagneticlike signatures but rather behave paramagnetic. Thus, the ferromagnetism in Gd:GaN is caused by polarization of the N site or by extrinsic mechanisms such as magnetic polarization of defects or residual oxygen in these samples.