The thermodynamics of the unitary (normalized spin) quantum and classical Ising models with skew magnetic field, for |J|β≲0.9, is derived for the ferromagnetic and antiferromagnetic cases. The high-temperature expansion (β-expansion) of the Helmholtz free energy is calculated up to order β7...

We study the thermal properties of the quantum and classical models of the Fe4 and Fe8 SMMs in the presence of an arbitrary constant magnetic field, obtaining the β-expansions of the Helmholtz free energy of the models up to orders β26, β25 and β26 for the spin-5 (Fe4), the spin-10 (Fe8) and...