High-pressure Mossbauer spectroscopy of perovskite high valence iron oxides under external magnetic field

The magnetic properties of SrFeO3 (SFO), CaFeO3 (CFO) and Sr2/3La1/3FeO3 (SLFO), which are perovskite iron oxides with a high valence state of Fe, have been investigated by high-pressure Mossbauer spectroscopy under external magnetic field. These perovskite oxides have been found to switch electronic ground state drastically from the antiferromagnetic (AF) state to the ferromagnetic (FM) state under high pressure. CFO and SLFO, which show a charge-disproportionation (CD: 2Fe(4+) -> Fe3+ + Fe5+ and 3Fe(11/3+) -> 2Fe(3+) + Fe5+, respectively) at low temperature, switch magnetic ordering from the AF state to the FM state simultaneously with the suppression of the CD in a critical pressure of about 19 and 23 GPa, respectively. SFO, which does not show any CD, switches its magnetic ordering from the AF state to the FM state at about 7 GPa. These pressure-induced transitions from the AF state to the FM state are accompanied by the discontinuous reduction of the magnetic hyperfine fields.