Vacancy Induced Magnetism in Tetragonal Structure ZrO₂ Based on First-Principles Study

Tetragonal zirconia (t-ZrO₂) has broad applications for structural ceramics, such as solid oxide fuel cells, electrolysis materials, membranes, and biomedical applications. However, its electronics and magnetics properties are rarely well studied. We carried out spin-polarized calculations to understand the vacancy characteristics in t-ZrO₂. We apply neutral single Z_r vacancy (V_Zr) and O vacancy (VO) for supercell calculations up to 108 atoms. The calculated band gap of t-ZrO2 is 3.81 eV, which becomes a narrowing band gap by V_Zr. We find that both vacancies systems induce outward relaxations of atoms near vacancies, creating lower symmetry from pristine D_4h to D_2d and C_2v for V_Zr and V_O cases, respectively. The calculated magnetic moment VZr is 4 µB due to four electrons of the valence band being occupied in the majority state. Four oxygen electrons of p-orbitals dominate the spin densities near VZr. In contrast, the magnetic moment in the case of VO is 0 µB. Thus, since they have a high magnetic moment in the case of V_Zr, t-ZrO₂ is potentially used as material for diluted magnetic semiconductors.