INDIRECT EXCHANGE INTERACTIONS IN CUBIC LANTHANIDE SESQUIOXIDES

Neel temperatures have been calculated for eight cubic lanthanide sesquioxides (C-Ln2O3) on the assumption that the magnetic ordering energy originates from indirect exchange interactions between nearest-neighbour Ln3+ ions via 5d conduction electrons. The Anderson model of exchange in insulators has been applied where the transfer integral has been taken proportional to the overlap integral between 4f wavefunctions. The results indicate that the indirect exchange represents in most cases 15 to 70% of the observed magnetic transition energy. The set of cation-cation distances for the whole series of C-Ln2O3 is reported for the first time.