High pressure experiments with synchrotron radiation

Using a diamond anvil cell (DAC), high pressure 57Fe Mössbauer spectroscopy has been performed with the nuclear forward scattering of synchrotron radiation. We used monochromatized synchrotron radiation from an in‐vacuum type undulator as a high‐density strong Mössbauer source with a quite small beam size. Pressure‐induced magnetic hyperfine interactions at 57Fe in SrFeO2.97 has been detected at 74 GPa by a quantum‐beat modulation of the decay rate after collective nuclear excitation with the synchrotron radiation pulse. Evidence for a transition from antiferromagnetism to ferromagnetism of Fe in SrFeO2.97 at 74 GPa and 300 K has been obtained from the nuclear forward scattering under a transverse magnetic field.