THERMODYNAMIC MEASUREMENTS IN MAGNETICALLY ORDERED SOLID HE-3

Measurements of the melting pressure and constant-volume pressure of solid He-3 have been made in the vicinity of the various magnetic-ordering transitions. Data have been obtained at several magnetic fields for both the low-field phase and the high-field phase, with particular attention given to the region of the polycritical point. The absence of a latent heat indicates that the transition from the paramagnetic to the high-field phase is second order or lambda-type. A spin-wave velocity of 6.95 cm/sec was obtained from the T4 temperature dependence of the melting pressure in the high-field phase for B = 0.495 T. These data provide the entropy and volume discontinuities as functions of field along the first-order low-field phase boundary. The volume dependence of the transition temperatures has been extracted from these and other data.