In response to recent experimental reports of unexpected ferromagnetism in thin films, first-principles investigations were made of magnetic order, possibly brought about by the presence of small concentrations of intrinsic point defects. Ab initio electronic structure calculations, using density functional theory, showed that isolated cation vacancy sites in HfO2 led to the formation of high-spin defect states. Furthermore, these appeared to be ferromagnetically coupled with a rather short range magnetic interaction, resulting in a ferromagnetic ground state for the whole system. The occurrence of these high-spin states and ferromagnetism was found in the low-symmetry monoclinic phase of HfO2. This was radically different to other systems which were known to exhibit point defect ferromagnetism.

Ferromagnetism Driven by Intrinsic Point Defects in HfO2. C.D.Pemmaraju, S.Sanvito: Physical Review Letters, 2005, 94[21], 217205 (3pp)