Exact results of the one-dimensional tranverse Ising model in an external longitudinal magnetic field

TL;DR

This paper provides exact analytical results for the magnetic properties of a one-dimensional mixed spin-1/2 and spin-S transverse Ising model under an external longitudinal magnetic field, revealing complex thermal behaviors.

Contribution

It introduces an exact solution for the 1D mixed spin transverse Ising model with an external field using decoration-iteration transformation, including detailed thermodynamic properties.

Findings

Exact expressions for Gibbs free energy, magnetizations, entropy, and specific heat.

Identification of non-trivial thermal dependencies of transverse magnetization.

Evidence of spin reorientation from longitudinal to transverse field in a narrow temperature range.

Abstract

Magnetic properties of the 1D mixed spin-1/2 and spin-S (S >1/2) transverse Ising model in the presence of an external longitudinal magnetic field are calculated exactly by the use of the generalised decoration-iteration mapping transformation. By assuming that only the spin-S atoms do interact with the transverse field the exact results for the Gibbs free energy, longitudinal magnetization, transverse magnetization, entropy and specific heat have been derived and discussed in detail. In addition to the standard temperature variations of the transverse magnetization, another two non-trivial thermal dependences have been found. The results support the concept that the spin reorientation from the longitudinal towards the transverse field direction takes place in the narrow temperature region.