Dresden 2020 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 60: Magnetic Coupling and Anisotropy in Thin Films (joint session MA/DS)
MA 60.3: Vortrag
Freitag, 20. März 2020, 10:00–10:15, HSZ 04
Titanium d-ferromagnetism with perpendicular anisotropy in defective anatase — •Markus Stiller1, Alpha T. N'Diaye2, Hendrik Ohldag2, José Barzola Quiquia1, Pablo D. Esquinazi1, Thomas Amelal3, Carsten Bundesmann3, Daniel Spemann3, Martin Trautmann4, Angelika Chassé4, Hichem Ben Hamed4, Waheed A. Adeagbo4, and Wolfram Hergert4 — 1Felix-Bloch-Institute for Solid-state Physics, University of Leipzig, Germany — 2ALS, Lawrence Berkeley National Laboratory, USA — 3Leibniz Institute of Surface Engineering, Germany — 4Institute of Physics, Martin-Luther-Universität Halle-Wittenberg, Germany
Undoped TiO2 anatase thin films were grown on LAO and STO substrates. Ferromagnetism was generated at the surface of anatase films by low-energy ion irradiation. Ar+-ion irradiation resulted in a thin (10nm) ferromagnetic surface layer. Field hysteresis as well as zero-field cooled and field cooled curves reveal that, after irradiation the samples show ferromagnetism at room temperature with an out-of-plane easy axis and low remanence. Magnetic force microscopy reveals that this low remanence is due to oppositely aligned magnetic domains. XMCD measurements at room temperature show that the band at the titanium L-edges is spin polarized, not at the O K-edge. Together with DFT calculations, the results indicate that Ti vacancy-interstitial pairs are responsible for the magnetic order. These results open up interesting possibilities for future applications, e.g. single domain patterns of μm size can be easily prepared. Further, they contradict the theory of paramagnetism due to vacuum fluctuations proposed by Coey.