Temperature dependence of the upper critical field in bcc solid 3He

The temperature dependence of the upper critical field for the antiferromagnetic high-field phase of bcc solid He-3 has been calculated by Iwahashi and Masuda utilizing the Green-function method with Tyablikov decoupling. In the low temperature limit the upper critical field, H-c2(T), is found to decrease from H-c2(0) with increasing temperature as a power law with exponent 3/2. Interestingly, the same power law dependence has been predicted for a system of dilute magnons undergoing Bose-Einstein condensation and has been observed in the spin-gap antiferromagnets TlCuCl3, BaCuSi2O6, and NiCl2-4SC(NH2)(2). An experiment has been attempted to determine precisely the temperature dependence of the upper critical field in bcc solid He-3 by measuring the pressure of the solid during adiabatic demagnetization through the critical field. The theoretical framework motivating the experimental study is presented along with details of the experimental setup.