Modified strong-coupling treatment of a spin-1/2 Heisenberg trimerized chain
Institute for Condensed Matter Physics, NASU, 1 Svientsitskii Street, L’viv-11, 79011 Ukraine
Quantum spin-1/2 antiferromagnetic Heisenberg trimerized chain with strong intradimer and weak monomer-dimer coupling constants is studied using the many-body perturbation expansion developed from the exactly solved spin-1/2 Ising-Heisenberg diamond chain. Within the suggested approach we obtain the effective Hamiltonians for the magnetic-field range from zero to one-third plateau, and from one-third plateau to the saturation magnetization. It is shown that the derived effective Hamiltonian provides at low enough temperatures sufficiently accurate results for magnetization curves and thermodynamic properties. Using the results for the effective Hamiltonian, we additionally suggest a straightforward procedure for finding the microscopic parameters of one-dimensional trimerized magnetic compounds with strong intradimer and weak monomer-dimer couplings.