Magnetism in TiO2 from ab initio perspective
| Authors | |
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| Year of publication | 2023 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | We present a combined experimental and theoretical study of surface-related magnetic states in TiO2. Our experiments on nano-sized thin films of pure TiO2 have suggested that the observed room-temperature magnetism originates from defects, in particular, from the surface of thin films as well as from point defects, such as oxygen vacancies located mainly at the surface. Since verifying this issue is very important to be able to manipulate the magnetic properties of pristine TiO2 films for future spintronic applications, certain conclusions from theoretical work is very demanding. Therefore, quantum-mechanical density functional theory (DFT) calculations were subsequently performed for (i) bulk anatase TiO2, (ii) bulk-like TiO2-terminated vacancy-free (001) surfaces, (iii) vacancy-containing TiO-terminated (001) surfaces, (iv) TiO_0.75-terminated (001) surfaces with additional 25% surface oxygen vacancies, as well as (v) oxygen-terminated (001)-surfaces. Our fixed-spin-moment calculations identified both the bulk and the bulk-like terminated vacancy-free TiO2-terminated (001) surfaces as non-magnetic. In contrast, oxygen vacancies in the case of TiO-terminated and TiO_0.75-terminated (001) surfaces lead to ferromagnetic and rather complex ferrimagnetic states, respectively. The spin-polarized atoms are the Ti atoms (due to the d-states) located in the surface and sub-surface atomic planes. Lastly, the O-terminated surfaces are also magnetic due to the surface and sub-surface oxygen atoms and sub-surface Ti atoms (but their surface energy is high). |
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