Electronic structure and exchange interactions of the ladder vanadates CaV2O5 and MgV2O5

We have performed ab initio calculations of the electronic structure and exchange couplings in the layered vanadates CaV2 O5 and MgV2 O5 . On the basis of our results we provide a possible explanation of the unusual magnetic properties of these materials, in particular the large difference in spin gap between CaV2 O5 and MgV2 O5 .