Series expansion for an easy-plane spin-one ferromagnet

Abstract
Series for susceptibility and zero-field specific heat have been obtained to the fourth order in βJ or JD for an easy-plane spin-one ferromagnet. The series expansions are for a general lattice and for exchange interaction of arbitrary range. The single-ion anisotropy is treated exactly. We outline the method of series expansion and discuss the critical quantities deduced from the series obtained.