Phase Diagram of the Spin-1 XXZ Heisenberg Ferromagnet with a Single-Ion Anisotropy

Jozef Strečka；Ján Dely；Lucia Čanová

Chinese Journal of Physics

46卷3期（2008 / 06 / 01）

329 - 337

英文

The phase diagram of the spin-1 quantum Heisenberg model with both exchange as well as single-ion anisotropy is constructed, within the framework of the pair approximation formulated as a variational procedure based on the Gibbs-Bogoliubov inequality. In this form the adapted variational approach is used to obtain results equivalent to the Oguchi pair approximation. It is shown that the single-ion anisotropy induces a tricritical behavior in the model system considered, and the location of the tricritical point is found in terms of its dependence on the exchange anisotropy strength.