1H-NMR studies on spin dynamics in molecular nanomagnet V15

Abstract 1 H-NMR study of a molecular magnet K 6 [V 15 As 6 O 42 (H 2 O)]8H 2 O (in short, V15) provides evidences for a gradual slowing of fluctuations of the V 4+ spins with increasing magnetic field. The temperature and magnetic field dependence of 1/ T 1 is well explained by a model in terms of spin phonon interaction in the magnetic field region ( H >2.7 T) where the ground state of the V15 cluster is S = 3 2 . On the other hand, the T 1 data is not reproduced by the model in the low magnetic field region where the ground state is formed by two S = 1 2 doubly degenerate states, suggesting importance of additional contribution to the spin dynamics of V 4+ moments due to peculiarities of the S = 1 2 triangle configuration in the V15 cluster.