Exchange-transfer in mixed-valence clusters with one migrating hole

A new mechanism for exchange-transfer specific to hole-type mixed-valence clusters is proposed. The intermediate state in the second-order exchange-transfer process is achieved by the jump of the electron from the spin-core of the d(n+1) ion into the empty orbital of the d(n) ion. As distinguished from the mixed-valence clusters with one delocalized electron this intermediate state is the high-spin one giving rise to a ferromagnetic contribution to the ground manifold. On the basis of angular momentum theory a general solution of the exchange-transfer problem is given for arbitrary nuclearity mixed-valence hole-type clusters with many-electron paramagnetic spin-cores. The interplay between the double exchange, exchange-transfer and Heisenberg exchange is considered in detail for the simple case of a d(2)-d(2)-d(1) trimer.