THE EFFECT OF PRESSURE ON THE FERROMAGNETIC PHASE TRANSITION OF EuO

The compressions of EuO up to 10 000 atm have been measured at 296 °K, 82 °K, and 4.2 °K. The shift in temperature of the ferromagnetic phase transition has been measured as a function of pressure by measuring the mutual inductance of a coil containing the solid. The transition occurs at about 72 °K at 10 000 atm, which is about 5 °K higher than the transition at atmospheric pressure. The results tend to substantiate the molecular field model for EuO proposed by McGuire and Shafer. An estimate is made of the variation of the exchange interaction parameter with lattice parameter, ΔJ1/Δa = −0.62 °K/Å, where J1 refers to interactions between nearest magnetic neighbors.