Double exchange in distorted trimeric mixed-valence clusters Original Research Article

The joint Heisenberg and double exchange model for trimeric mixed-valence clusters is considered with the taking into account (1) the δ difference of the exchange Jdn−dn and Jdn−dn±1 parameters in trigonal and distorted trimers and (2) the difference of the electron (hole) transfer parameters in distorted clusters. In the trigonal trimer, the δ difference leads to the splitting of the exchange-resonance levels degenerated in the model with δ = 0. The δ exchange difference does not change trigonal symmetry of the states of MV cluster with the electron (hole) delocalized among the three metal sites. The distortions result in non-linear dependence of the energy on the double exchange parameter and in the essential change of the low-temperature behavior of magnetic moment of MV trimeric clusters. The taking into account the difference of the electron transfer parameters tij in distorted system leads to the splittings of the trigonal resonance transfer states on the levels of more lower symmetry.