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...

We revisit the method of calculating the β-expansion of the Helmholtz free energy of any one-dimensional (1D) Hamiltonian with invariance under space translations, presented in [O. Rojas, S.M. de Souza, M.T. Thomaz, J. Math. Phys. 43 (2002) 1390], extending this method to 1-D Hamiltonians that...