Four-Spin Exchange Model andHe3Magnetism

Abstract

A two-parameter model based on three-spin exchange and planar four-spin exchange gives at low field a first-order transition to the ordered phase suggested by Osheroff, Cross, and Fisher and at high field gives a second-order phase agreeing with the experiments of Godfrin et' al. and Adams et al. It also fits well the high-temperature expansion coefficients and the susceptibility of the low-field phase.