Room temperature ferromagnetism was characterized for thin films of SrTi0.6Fe0.4O3−δ grown by pulsed laser deposition on SrTiO3 and Si substrates under different oxygen pressures and after annealing under oxygen and vacuum conditions. X-ray magnetic circular dichroism demonstrated that the magnetization originated from Fe2+ cations, whereas Fe3+ and Ti4+ did not contribute. Films with the highest magnetic moment (0.8 {\mu}B per Fe) had the highest measured Fe2+:Fe3+ ratio of 0.1 corresponding to the largest concentration of oxygen vacancies ({\delta} = 0.19). Post-growth annealing treatments under oxidizing and reducing conditions demonstrated quenching and partial recovery of magnetism respectively, and a change in Fe valence states. The study elucidates the microscopic origin of magnetism in highly Fe-substituted SrTi1−xFexO3−δ perovskite oxides and demonstrates that the magnetic moment, which correlates with the relative content of Fe2+ and Fe3+, can be controlled via the oxygen content, either during growth or by post-growth annealing.
@article{arxiv.1906.00509,
title = {An XMCD study of magnetism and valence state in iron-substituted strontium titanate},
author = {Astera S. Tang and Jonathan Pelliciari and Qi Song and Qian Song and Shuai Ning and John W. Freeland and Riccardo Comin and Caroline A. Ross},
journal= {arXiv preprint arXiv:1906.00509},
year = {2019}
}