HfO$_2$: a new direction for intrinsic defect driven ferromagnetism

TL;DR

This study uses first principles calculations to explore how intrinsic point defects in HfO₂ thin films can induce ferromagnetism, revealing defect-induced magnetic states and interactions specific to the monoclinic phase.

Contribution

It demonstrates that intrinsic cation vacancies in HfO₂ can produce ferromagnetic states, a novel insight into defect-driven magnetism in this material.

Findings

Cation vacancies lead to high spin defect states.

Defect states are ferromagnetically coupled.

Ferromagnetism occurs in the monoclinic phase.

Abstract

In view of the recent experimental reports of unexpected ferromagnetism in HfO$_{2}$ thin films, we carried out first principles investigations looking for magnetic order possibly brought about by the presence of small concentrations of intrinsic point defects. {\it Ab initio} electronic structure calculations using density functional theory (DFT) show that isolated cation vacancy sites in HfO$_{2}$ lead to the formation of high spin defect states. Furthermore these appear to be ferromagnetically coupled with a rather short range magnetic interaction, resulting in a ferromagnetic ground state for the whole system. More interestingly, the occurrence of these high spin states and ferromagnetism is in the low symmetry monoclinic phase of HfO$_{2}$. This is radically different from other systems previously known to exhibit point defect ferromagnetism, warranting a closer look at the phenomenon.