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 3He has been calculated by Iwahashi and Masuda utilizing the Green-function method with Tyablikov decoupling. In the low temperature limit the upper critical field, Hc2(T), is found to decrease from Hc2(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 3He 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.