Magnetism of Quantum Solid with Strong Zero Point Lattice Vibration

Abstract

In quantum solids of fermions such as solid ³He, where a tunneling motion for particle exchange is enhanced by zero-point vibrations, there is a possibility that a hybrid of the exchange tunneling and the zero-point vibration may lead to unforeseen magnetic properties, which are outside the scope of the Heisenberg model. The simplest model is adopted for the hybridization. In this model the exchange interactions are assumed to exist only for the nearest neighbor pairs and a pair spin interaction is supposed to grow sufficiently large when the n.n. bond expands in the vibrational motion. The spin-phonon interactions, which are off-diagonal in the phonon representation, are shown to produce remarkable effects on the magnetic field dependence of pressure, on the specific heat, on the susceptibility and on the mechanism leading to exotic spin order such as uudd.