Mossbauer spectroscopic study of FeS under pressure using synchrotron radiation

The delay-time spectra of Fe-57 nuclear resonant forward scattering in FeS which belongs to the boundary between the charge-transfer and Mott-Hubbard insulators have been observed under high pressure up to about 6 GPa at BL09 XU in SPring-8. Tile observed beat pattens in delay-time spectra are distin guished two different types which correspond to the two different phases. W e have successfully applied the maximum-entropy method to analyze the obser ved delay-time spectra. The frequencies of quantum beats which directly dep end on the energy differences between two hyperfine splitting levels of Fe- 57 nuclei were extracted by this analysis and then the hyperfine interactio n parameters were determined from there extract-ed frequencies. Since the e valuated magnetic hyperfine field at; 0.1MPa is smaller than that at 2 GPa, the Neel temperature of FeS with a troilite structure increases with press ure.