Interplay between R 4 f and Fe 3d states in charge-ordered RFe2O4 (R = Er, Tm, Lu)

Abstract

The electronic structures of R 4f and Fe 3d states of RFe2O4 (R = Er, Tm, Lu) have been investigated by employing soft x-ray absorption spectroscopy (XAS) and magnetic circular dichroism at the Fe 2p and R 3d absorption edges. It is found that the valence states of Fe and R ions are nearly Fe2.5+ and R3+, and that the net magnetic moments of Fe2+ and Fe3+ ions are antiparallel to each other. Both R 3d and O 1s XAS spectra show that the localized R 4f states do not contribute to the multiferroicity of RFe2O4. On the other hand, the magnetization data for RFe2O4 at low temperature (T) reveal the cluster glass behavior for R = Tm and Lu, but not for R = Er. This work suggests that the T-dependent structural differences among RFe2O4, caused by different R ions, are closely related to the magnetoelectricity at low temperature.