57 Fe Mössbauer spectroscopy in an applied magnetic field has been conducted on single crystals of CuFeO2 and CuFe 0.965Ga0.035O2 in order to investigate magnetic-field-induced ferroelectric states. The Mössbauer spectra observed under a magnetic field change significantly, corresponding to magnetic- field-induced phase transitions. In the ferroelectric incommensurate (FEIC) phase (7 < Hex < 13 T), the spectrum can be explained by a model with spins distributed at approximately 20, 95, and 160° from the c-axis in the (110) plane. This spin configuration resembles the "complex noncollinear spin configuration (CNC) " model proposed theoretically. In the FEIC phase, the isomer shift is larger, while the quadrupole splitting and average hyperfine field are smaller than those in the collinear four sublattice (4SL, 0 < Hex < 7 T) and five sublattice (5SL, H ex > 13 T) phases. In addition, a noticeable change in the hyperfine field is observed with varying magnetic fi eld. We consider that these changes indicate the change in the electronic state of the Fe3+ ion, possibly modified by a spin-orbit interaction.
ASJC Scopus subject areas
- Physics and Astronomy(all)