Irreducible tensor operator method study on molecular magnetism: A practical approach and its use for high-nuclearity magnetic cluster

A general form of the effective Hamiltonian was introduced to solve the complex magnetic exchange system. On the basis of the irreducible tensor operator method a new practical approach was suggested, and accomplished by the BJMAG package. Potentiality of the new approach to isotropic Heisenberg spin clusters was tested through two high-nuclearity clusters.