Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films

• Main Authors: M. Stiller, J. Barzola-Quiquia, P. Esquinazi, D. Spemann, J. Meijer, M. Lorenz, M. Grundmann
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2016-12-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.4971794

The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.