Room temperature ferromagnetism of zinc oxide: a grain boundary phenomenon?

Zink oxide doped with Cobalt shows ferromagnetic behavior at room temperature. Our X-ray Magnetic Circular Dichroism measurements clearly demonstrate that none of the sample’s elements (Co, Zn or O) is responsible for ferromagnetism. Dedicated data evaluation from literature and our own investigations indicate that ferromagnetism only appears in nanocrystalline ZnO and is likely induced by Oxygen defects located in the dense grain boundary network. These findings may open promising perspectives for new technological applications.