Abstract
The spin states at the surface of epitaxial thin films of hematite, both undoped and doped with 1% Ti, Sn, or Zn, respectively, were probed with x-ray magnetic linear dichroism (XMLD) spectroscopy. Morin transitions were observed for the undoped K) and Sn-doped K) cases, while Zn- and Ti-doped samples were always in the high- and low-temperature phases, respectively. In contrast to what has been reported for bulk hematite doped with the tetravalent ions and , for which dramatically decreases, these dopants substantially increase in thin films, far exceeding the bulk values. The normalized Fe -edge dichroism for does not strongly depend on doping or temperature, except for an apparent increase of the peak amplitudes for K. We observed magnetic field-induced inversions of the dichroism peaks. By applying a magnetic field of 6.5 T on the Ti-doped sample, a transition into the state was achieved. The temperature dependence of the critical field for the Sn-doped sample was characterized in detail. It was demonstrated the sample-to-sample variations of the Fe -edge spectra were, for the most part, determined solely by the spin orientation state. Calculations of the polarization-dependent spectra based on a spin-multiplet model were in reasonable agreement with the experiment and showed a mixed excitation character of the peak structures.
1 More- Received 8 January 2017
- Revised 9 July 2017
DOI:https://doi.org/10.1103/PhysRevB.96.094426
©2017 American Physical Society