Date of Original Version
New analytic results are presented for the low-T thermodynamics of the Ising-Heisenberg linear ferromagnetic in a magnetic field H0. For small H0 the thermodynamic functions show unexpected and interesting structure as a function of H0 and the anisotropy Δ. The thermal and magnetic energy gaps have singularities, not necessarily at the same Δ−H0 location, as changes occur in the type of excitation dominating the low-T behavior. The results may relate to quantum solitons in the linear ferromagnet.
Johnson, J. D., & Bonner, J. C. (1980). Excitation spectrum and thermodynamic properties of the Ising-Heisenberg linear ferromagnet. Phys. Rev. Lett. 44(9), 616-619. doi: 10.1103/PhysRevLett.44.616
Available at: http://dx.doi.org/10.1103/PhysRevLett.44.616