Kinetic exchange Hamiltonian for orbitally degenerate ions

A new approach to the problem of the kinetic exchange for orbitally degenerate ions is developed. The highly anisotropic effective Hamiltonian is expressed in terms of unit irreducible tensor operators and spin operators, All parameters of the exchange Hamiltonian are expressed through relevant transfer integrals, crystal field and Racah parameters for the metal ions. As an example the edge-shared (D-2h) bioctahedral cluster is discussed and some comments on the considerations of Anderson, Goodenough and Kanamori and McConnell are given. (C) 1998 Elsevier Science B.V.