Quantum-classical crossover of the escape rate of a biaxial spin system with an applied magnetic field

摘要

Employing the method of mapping the spin problem onto a particle one developed by Ulyanov and Zaslavskii, we derive the effective Hamiltonian for a biaxial spin system with an applied magnetic field along the medium axis and find an analytical form of the phase boundary line between first and second order transitions, from which a complete phase diagram can be obtained. We also derive an analytical form of the crossover temperature as a function of the scaled anisotropy constant at the phase boundary. (C) 2001 Elsevier Science B.V. All rights reserved. [References: 27]