NANOMETER-SCALE MOLECULAR CLUSTER V15: EPR AND ADIABATIC MAGNETIZATION

ABSTRACT. In this article we analyze EPR and adiabatic magnetization of the nanoscopic V15 cluster exhibiting a triangular VIV3 array causing spin frustration. A model of V15 includes isotropic exchange interaction and antisymmetric (AS) exchange in the general form compatible with the trigonal symmetry. Orientation of the AS vector (but not its absolute value) is shown to play an important physical role in spin-frustrated systems. We were able to reach perfect fit to the experimental data on the stepwise dependence of magnetization vs. field at ultra-low temperatures. Furthermore, it was possible for the first time to estimate precisely two components of the AS vector coupling constant, namely, in-plane component and the perpendicular part. We show that only intramultiplet transitions in EPR are allowed when the vector of AS exchange is normal to the plane of vanadium triangle, meanwhile the in-plane part of AS exchange gives rise to a series of weak intermultiplet transitions. Experimental data on high-frequency EPR of V15 at low temperatures are discussed