X-ray Magnetic Circular Dichroism Investigations of the Origin of Room Temperature Ferromagnetism in Fe-Doped ZnO Nanoparticles

We have studied the electronic structure of Zn0.9Fe0.1O nanoparticles, which have been reported to be ferromagnetic at room temperature, by using soft X-ray absorption (XAS) and magnetic circular dichroism (XMCD). The XAS results indicate that Fe ions are predominantly in the Fe3+ state with mixture of a small amount of Fe2+. It is shown that the room temperature ferromagnetism in the Zn0.9Fe0.1O nanoparticles is primarily originated from the antiferromagnetic coupling between unequal amounts of Fe3+ ions occupying two sets of nonequivalent positions in the region of the XMCD probing depth of ~2–3 nm.