Thin films: unexpected magnetism in a dielectric oxide.

Venkatesan, M; Fitzgerald, C B; Coey, J M D · Nature · 2004

basic_science · Level V

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Abstract

It is generally accepted that magnetic order in an insulator requires the cation to have partially filled shells of d or f electrons. Here we show that thin films of hafnium dioxide (HfO2), an insulating oxide better known as a dielectric layer for nanoscale electronic devices, can be ferromagnetic even without doping. This discovery challenges our understanding of magnetism in insulators, because neither Hf4+ nor O2- are magnetic ions and the d and f shells of the Hf4+ ion are either empty or full.