Charge Disproportionation and Magnetic Order of CaFeO3under High Pressure up to 65 GPa

Using a diamond anvil cell, 57 Fe Mössbauer spectroscopy has been carried out on the perovskite oxide CaFeO 3 under high pressures up to 65 GPa at various temperatures. The critical temperature of a charge disproportionation (CD: 2Fe 4+ →Fe 3+ + Fe 5+ ) 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 an ambient pressure rises to 400 K at 34 GPa without the CD, which suggests that the different charged particles control the charge and spin order separately in CaFeO 3 .