Yoshikazu Takeda

Mössbauer study of CaFeO3 under external high—Pressure

Abstract57Fe Mössbauer and X-ray diffraction measurements have been performed on a perovskite CaFeO3 under external high pressure upto 50 GPa at room temperature using a diamond anvil cell. Above 29 GPa the57Fe magnetic hyperfine splitting appears superimposing with usual paramagnetic pattern of CaFeO3. Magnitude of hyperfine field is 16 T and much smaller than 33 T of typical Fe4+ in SrFeO3 suggesting a transition from high-spin S=2 to low-spin S=1 state in CaFeO3.

57Fe Mössbauer study of SrFeO3 under ultra-high pressure

Abstract57Fe Mössbauer absorption spectra under ultra-high pressure up to 53 GPa have been measured using a diamond anvil cell for SrFeO2.97 which is one of the typical Fe4+ oxides having a cubic perovskite structure. External high pressure up to 53 GPa makes no indication of structural transformation and does not show any change in valence state of iron, however the Néel temperature of 131 K at 0 GP increases to 300 K and the57Fe magnetic hyperfine field decreases from 32.9 T at 0 GPa and 6.5 K to 23.3 T at 53 GPa and 300 K.

High-pressure Mössbauer study of perovskite iron oxides

Abstract Using a diamond anvil cell, 57Fe Mossbauer measurements for perovskite iron oxides of SrFeO3 have been performed under high pressure up to 53 GPa at room temperature. SrFeO3 does not show any transition up to 53 GPa maintaining a cubic perovskite structure with Fe4+, but it is found by the measurement under external magnetic field the helical spin structure of antiferromagnetic changes to collinear ferromagnetic spin structure.