High‐pressure 57Fe Mössbauer study of Fe3O4 at 298 K

Abstract

At 298 K, 57Fe Mössbauer spectra of Fe3O4 exhibit an increase in complexity with increasing pressure in the range 1×105 to 5×109 Pa. There is an incipient splitting of the B‐site pattern into two components with relative intensities of 3 : 1. For the more intense pattern, Hn is 462 kOe and 470 kOe at 1×105 and 5×109 Pa, respectively; the corresponding values for the less intense patterns are 454 and 448 kOe. The B‐site electric quadrupole interactions also exhibit appreciable changes. The A‐site pattern exhibits no qualitative changes in line profiles and only modest changes in the hyperfine interaction parameters are observed. For example, at 1×105 and 5×109 Pa, Hn is 492 and 490 kOe, respectively; the corresponding isomer‐shift values are 0.258 and 0.233 mm s−1. These results are consistent with the broadening of the lines of the B‐site patterns at ambient temperature and pressure arising from the different relative orientations of the direction of magnetization and of the axes of the electric field gradient tensor.