Magnetic and structure transition of MnFeO solid solutions under high-pressure and high-temperature conditions

Yamanaka, Takamitsu*; Hirao, Naohisa*; Nakamoto, Yuki*; Mikouchi, Takashi*; Hattori, Takanori   ; Komatsu, Kazuki*; Mao, H.-K.*

Magnetic and crystal structure of MnFeO solid solutions under high-PT conditions are investigated by neutron diffraction and synchrotron Mssbauer spectroscopy. The ferrimagnetic-paramagnetic transition and tetragonal-cubic transition of MnFeO spinel occur at 100C and 180C, respectively, suggesting both the transitions are not coupled. The structure transition temperature decreases with pressure. Mssbauer experiments and neutron diffraction revealed that the Fe occupancy in tetrahedral site increases increase with pressure, suggesting MnFeO phase approaches inverse spinel. Magnetic structure refinement clarified paramagnetic and ferrimagnetic structure of MnFeO and MnFeO. These spinels transform into high-pressure orthorhombic phases at 18.4 and 14.0 GPa, respectively, indicating lower transition pressure with increasing Mn content.