Quantum-classical phase transition of the escape rate of two-sublattice antiferromagnetic large spins

Abstract

The Hamiltonian of a two-sublattice antiferromagnetic spins, with single (hard-axis) and double ion anisotropies described by $H=J{\hat{\mathbf{S}}}_1\cdot {\hat{\mathbf{S}}}_2-2J_z{\hat{S}}_{1z}{\hat{S}}_{2z}+K({\hat{S}}_{1z}^2+{\hat{S}}_{2z}^2)$ is investigated using the method of effective potential. The problem is mapped to a single particle quantum-mechanical Hamiltonian in terms of the relative coordinate and reduced mass. We study the quantum-classical phase transition of the escape rate of this model. We show that the first-order phase transition for this model sets in at the critical value $J_c=\frac{K+J_z}{2}$ while for the anisotropic Heisenberg coupling $H=J(S_{1x}{S}_{2x}+S_{1y}{S}_{2y})+J_z{S}_{1z}{S}_{2z}+K(S_{1z}^2+S_{2z}^2)$ we obtain $J_c=\frac{2K-J_z}{3}$ . The phase diagrams of the transition are also studied.

7 pages, 3 figures

References in corpus (4)

• Quantum dynamics of the Neel vector in the antiferromagnetic molecular wheel CsFe8
• Single-ion versus two-ion anisotropy in magnetic compounds: A neutron scattering study
• Suppression of quantum tunneling for all spins for easy-axis systems
• Spin Wave Theory of Spin 1/2 XY Model with Ring Exchange on a Triangular Lattice