Experimental results of magnetization and magnetic susceptibility of the square spin lattice can be interpreted by using a Heisenberg Hamiltonian for a small 4×4 square lattice. We find that the agreement between theory and experiments is remarkable, as in the case with the one-dimensional...

By applying the method of hierarchy of algebras, we derive exact thermodynamic results of the square 4×4 lattice and of the linear ring of 16 s=12 spins described by an isotropic Heisenberg Hamiltonian. Next-nearest-neighbour interactions are taken into account. The entropy, the specific heat,...

Experimental results concerning magnetic susceptibility and heat capacity of the CuSb2O6 crystal, where the Cu2+ ions form chains interacting with strong short range antiferromagnetic (AF) intrachain and weak AF interchain interactions, can be interpreted in terms of small rings to which the...