A spin-1 transverse Ising model with longitudinal crystal field in a
longitudinal magnetic field is examined by introducing an effective field
approximation (IEFT) which includes the correlations between different spins
that emerge when expanding the identities. The effects of the crystal field as
well as the transverse and longitudinal magnetic fields on the thermal and
magnetic properties of the spin system are discussed in detail. The order
parameters, Helmholtz free energy and entropy curves are calculated numerically
as functions of the temperature and Hamiltonian parameters. A number of
interesting phenomena such as reentrant phenomena originating from the
temperature, crystal field, transverse and longitudinal magnetic fields have
been found.Comment: 11 pages, 15 figure
