Phase Transitions of the Bilayered Spin-S Heisenberg Model and Its Extension to Fractional Dimensions
arXiv:cond-mat/9511070
Abstract
We study the ground state and the phase transitions of the bilayered spin- antiferromagnetic Heisenberg model using the Schwinger boson mean field theory. The interplane coupling initially stabilizes but eventually destroys the long-range antiferromagnetic order. The transition to the disordered state is continuous for small , and first order for large . The latter is consistent with an argument based on the spin wave theory. The phase diagram and phase transitions in corresponding model in fractional dimensions are also discussed.
14 pages, 7 Postscript figures, LaTeX