Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.
@article{arxiv.0807.3424,
title = {Suppression of spin-state transition in epitaxially strained LaCoO_{3}},
author = {C. Pinta and D. Fuchs and M. Merz and M. Wissinger and E. Arac and A. Samartsev and P. Nagel and S. Schuppler},
journal= {arXiv preprint arXiv:0807.3424},
year = {2009}
}
Comments
5 pages, 5 figures, submitted to Physical Review B