Simulations of the low-dimensional molecular-based spin systems: dodecanuclear nickel ring

The numerical exact diagonalization technique exploiting the point-group symmetry is worked out for the anisotropic Heisenberg spin Hamiltonian with the ring geometry. It is applied in large-scale simulations to the supramolecule Ni12(O2CMe)12(chp)12(H2O)6(THF)6, yielding the low-level energy spectra as a function of the single-ion anisotropy D and the thermodynamic functions. The strength of the constant D is analysed and estimated at D/kB=1.5K. The results for the zero-field susceptibility and the field-dependent magnetization are presented and compared with experimental data.