High-pressure Moessbauer study of FeS with nuclear forward scattering of synchrotron radiation

The delay-time spectra of the nuclear resonant forward scattering for FeS were measured at ambient conditions with the sample not-enriched in 57Fe and under high pressure using the sample with enriched about 10 at.% 57Fe. The quantum beat modulations in observed delay-time spectra under pressure change with two successive first-order phase transitions at 3.5 and 6.5 GPa. We have successfully analyzed the beat patterns in delay-time spectra using the maximum entropy method and extracted the frequencies in each phase. These frequencies are in good agreement with those expected form the hyperfine interactions which values were estimated by the analysis of Moessbauer absorption spectra. This is the first successful attempt to apply the maximum entropy method in this field. (author)