EXCHANGE INTERACTIONS IN INSULATORS AND SEMICONDUCTORS .1. THE CATION ANION CATION 3-CENTER MODEL

In this paper we discuss the theory of superexchange. We show that a large number of (super)exchange mechanisms, which are used to explain the basic magnetic interactions in insulating and semiconducting transition metal and rare-earth compounds, can be derived from the same equation by using a single principle: in transition metal compounds the exchange takes place predominantly on the anion while in rare-earth compounds exchange takes place almost predominantly on the cation. In this way we get a unified theory for the exchange interaction between magnetic ions in these systems. © 1990.