MAGNETIC-PROPERTIES OF THE COUPLED LADDER SYSTEM MGV2O5

We present magnetic-susceptibility measurements on MgV2O5, a compound in which the vanadium oxide planes have the same topology as in CaV2O5 . The most striking property is that there is an energy gap of about 1 5 K, much smaller than in CaV2O5, where the values reported are of the order of 500 K. We show that this may be understood naturally in term s of the phase diagram of the frustrated coupled ladder system. This a nalysis leads to the prediction that MgV2O5 should have incommensurate dynamic spin fluctuations.