On the Possible Exchange Parameters of bcc Solid ³He

Abstract

Applying the spin wave theory to bcc solid 3He and taking into account interactions between spin waves, the free energy at finite temperatures, antiferromagnetic resonance frequency in the ordered phase and magnetic field strength where the transition from the uudd state to the pseudoferromagnetic state occurs, are calculated. If the exchange parameters are assumed to be K_P=K_F=−0.2471 mK and j_t=−0.1565 mK, large positive high temperature expansion coefficient e₃ determined from specific heat and pressure measurements by Fukuyama et al. and Sawada et al. can be explained. The temperature dependence of free energy between 0.3 and 0.7 mK determined by Osheroff et al. is also explained as a combined effect of the interactions between spin waves and thermal excitations of spin waves with various wave lengths.