Hysteresis loops and adiabatic landau-zener-stückelberg transitions in the magnetic molecule {V₆}

We have observed hysteresis loops and abrupt magnetization steps in the magnetic molecule {V₆}, where each molecule comprises a pair of identical spin triangles, in the temperature range 1-5 K for external magnetic fields B with sweep rates of several Tesla per millisecond executing a variety of closed cycles. The hysteresis loops are accurately reproduced using a generalization of the Bloch equation based on direct one-phonon transitions between the instantaneous Zeeman-split levels of the ground state (an S = 1/2 doublet) of each spin triangle. The magnetization steps occur for B ≈ 0, and they are explained in terms of adiabatic Landau-Zener-Stückelberg transitions between the lowest magnetic energy levels as modified by an intertriangle anisotropic exchange of order 0.4 K.