Isomer shift and magnetic properties of EuO under pressure

We have measured the Mössbauer effect of 151Eu in EuO at temperatures down to 4 K and pressures to 31 GPa. At ambient pressure EuO becomes ferromagnetic at TC=69 K; at 31 GPa, TC=105(2) K; and a maximum value of TC in the region 15–25 GPa is inferred. A Brillouin fit of the hyperfine-field-temperature data at 31 GPa gives a reduced magnetic moment compared to ambient although the magnitude of the saturation hyperfine field is not reduced. The isomer shift with pressure weakly supports the expectation of an intermediate-valence change with pressure above 14 GPa.