Magnetism in disordered HfO2 nanoparticles and thin films

In an ionic picture of HfO2, the Hf4+ ion has a closed shell (4f14) electronic configuration, and O2- also has possess a close shell (2s2, 2p6) configuration and, consequently, HfO2 would be nonmagnetic. As a result, the observation of strong anisotropy and ferromagnetism at or above room temperature in recent years has been intriguing because it hasn’t been associated with any transition metals that have partially occupied 3D shells. Additionally, spintronics would benefit if pure HfO2 exhibited high-temperature ferromagnetism. In this chapter, we provide a thorough analysis of the causes of ferromagnetism in pure HfO2 nanostructures as well as a mechanistic explanation of how defects (either Hf or O or both defects) cause the growth of local magnetic moments in HfO2 nanostructures.