Magnetic Properties and Structure of TiO2-Mn (0.73%) Nanopowders: the Effects of Electron Irradiation and Vacuum Annealing

M. Uymin ORCID logo , A. Minin ORCID logo , A. Yermakov, A. Korolyov, M. Balezin, S. Sokovnin ORCID logo , A. Konev ORCID logo , S. Konev, L. Molochnikov ORCID logo , V. Gaviko, A. Demin ORCID logo show affiliations and emails
Received: 01 October 2018; Revised: 18 October 2018; Accepted: 22 October 2018
Citation: M. Uymin, A. Minin, A. Yermakov, A. Korolyov, M. Balezin, S. Sokovnin, A. Konev, S. Konev, L. Molochnikov, V. Gaviko, A. Demin. Magnetic Properties and Structure of TiO2-Mn (0.73%) Nanopowders: the Effects of Electron Irradiation and Vacuum Annealing. Letters on Materials, 2019, 9(1) 91-96
BibTex   https://doi.org/10.22226/2410-3535-2019-1-91-96

Abstract

Appearance of oxygen vacancies in TiO2-Mn leads to a small ferromagnetic contribution in magnetizationNanopowder TiO2-0.73 % Mn was synthesized by the sol-gel method. Thermal treatment of the samples was carried out in vacuum at a temperature of 500°C. Magnetic properties were studied in the temperature range from 2 to 850 K. The effects of electron irradiation and vacuum annealing on the EPR spectra and magnetic properties of TiO2‑Mn powder are discussed. It was established that a part of manganese ions in the anatase crystal lattice interacts antiferromagnetically, which causes a decrease in magnetization as compared to the result of the calculation for non-interacting ions. Vacuum annealing leads to the formation of oxygen vacancies and, at the same time, to a noticeable increase in the ferromagnetic contribution to magnetization, especially, after preliminary electron irradiation. We assume that the ferromagnetic contribution to the magnetization appears either due to incomplete compensation of antiferromagnetically directed moments of manganese ions, or due to positive exchange interactions of Mn ions via defects in the TiO2 lattice. It is shown that the temperature of magnetic disordering in samples with a spontaneous magnetic moment exceeds 600°C.

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