Charge disproportionation and magnetic order of CaFeO3 under high pressure up to 65 GPa

Using a diamond anvil cell, Fe-57 Mossbauer spectroscopy has been carried out on the per ovskite oxide CaFeO3 under high pressures up to 65 GPa at various temperatures. The critical temperature of a charge disproportionation (CD: 2Fe(4+) --> Fe3+--> Fe5+) and a magnetic ordering have been determined as a function of pressure. The CD occurs at an almost constant temperature of about 290 +/- 3 K in the pressure range of 0-17 GPa. At an increase of the pressure above 20 GPa, the CD reaction is suppressed and its critical temperature reduces to lower than 6 K. On the other hand, the magnetic ordering temperature of 125 K at all ambient pressure rises to 400 K at 34 GPa without the CD, which suggests that the different charged particles control the cl-large and spin order separately in CaFeO3.