Exchange transfer in high-nuclearity mixed valence magnetic clusters: Theoretical approach and expected manifestations

Abstract We report here a general solution of the exchange transfer problem in the high-nuclearity mixed valence clusters containing arbitrary number of itinerant electrons. The concept of two kinds of exchange transfer, namely kinetic and potential, is introduced by analogy with basic Anderson's mechanisms of the magnetic exchange. The kinetic exchange transfer is treated as a second order transfer process between two centres through the excited state of a third centre. The potential exchange transfer is also considered as a three-centre interaction but in this case only the ground states of the constituent ions are involved. The actual parameters of the exchange transfer are expected to be of the same order of magnitude as those for the magnetic exchange. An efficient computational approach is proposed making it possible to build up the matrices of all kinds of exchange transfer interactions in a closed analytical form, expressing the matrix elements in terms of the relevant spin quantum numbers. As distinguished from the magnetic exchange the kinetic and potential contributions to the exchange transfer act independently and their parameters cannot be, in general, combined to give a joint parameter of the exchange transfer. The magnetic manifestations of the exchange transfer are considered for selected trimeric systems with different topologies (linear and trigonal) and different electronic shells involving either migrating electrons or holes. The magnetic nature of the ground state is found to depend on the topology of the system and on the sign of the double exchange parameter.