Pressure dependence of Néel transition in (Mg,Fe)O

Pressure dependence of Neel temperature (T N) in (Mg0.20Fe0.80)O, (Mg0.25Fe0.75)O, and (Mg0.30Fe0.70)O was newly measured up to 1.14 GPa, using superconducting quantum interference device magnetometer and piston–cylinder-type pressure cell under hydrostatic condition. The dT N/dP values of (Mg0.20Fe0.80)O, (Mg0.25Fe0.75)O, and (Mg0.30Fe0.70)O were determined as 4.0 ± 0.3, 2.7 ± 0.3, and 4.4 ± 0.4 K/GPa, respectively, in linear approximation; however, the T N deviated from the linearity under nonhydrostatic conditions. The compositional dependence of dT N/dP in (Mg1−X Fe X )O showed a rapid decay with increasing Mg components at X ≥ 0.75 and the trend ended at X = 0.70. The estimated Neel transition pressure at room temperature by extrapolating these linearities are very similar to the rhombohedral distortion determined by previous X-ray diffraction studies for X ≥ 0.75, which suggests that the rhombohedral phase of (Mg1−X Fe X )O (X ≥ 0.75) at room temperature is antiferromagnetic under hydrostatic conditions.