LOW-TEMPERATURE BEHAVIOR OF THE 6-STATE CLOCK MODEL WITH COMPETING INTERACTIONS

The phase diagram of the six-state clock model on a three-dimensional lattice, with first- and second-neighbour competing interactions along one direction, is analysed using a systematic low-temperature expansi on carried to all orders where necessary. A transfer-matrix method sim plifies the configurational analysis. We find that an infinite number of commensurate phases are stable near a zero-temperature multiphase p oint; a richer hierarchy of 'mixed' phases is found to be stable down to zero temperature than in the ANNNI model. The system corresponds to an XY model with infinite hexagonal anisotropy and may be relevant to rare-earth multilayers.