Spin-charge-orbital coupling in multiferroic LuFe2O4 thin films

We report optical, electronic, and electrical properties of LuFe2O4 thin films deposited on (001) sapphire and (111) YSZ substrates by electron beam deposition. The absorption spectra of LuFe2O4 thin films contain several electronic transitions above its direct energy band gap of similar to 2.18 eV at 300 K. The Fe2+ d to d on-site and O 2p to Fe 3d charge-transfer electronic transitions display a ferrimagnetic transition at similar to 235 +/- 5K and the charge-ordered transition at similar to 350 +/- 10K. Resistivity and the energy band gap also exhibit the two transitions, confirming a strong spin-charge-orbital coupling in the LuFe2O4 thin film. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4720401]