Fig. 8
Magnetic susceptibility and Mössbauer spectra of Fe4O5. a Temperature dependence of magnetic susceptibility and inverse magnetic susceptibility measured at different hydrostatic pressures in a field of 0.5 T under field cooling. b Evolution of Mössbauer spectra upon cooling at about 2–3 GPa. Broadening of the first (low-velocity) line of the sextet starting at 150 K indicates charge ordering. c Representative Mössbauer spectra of different phases of Fe4O5 collected at different pressures and temperatures. The spectrum of phase I can be refined by superposition of a paramagnetic doublet (blue) assigned to iron in the trigonal prisms and a magnetic sextet (orange) assigned to Fe in the octahedra in a mixed-valence state. The spectra of phases II and III exhibit a complex distribution of hyperfine fields and can be refined by superposition of sextets
