Rabi oscillations in the V_15 Single Molecule Magnet (SMM) embedded in the surfactant DODA have been studied at different microwave powers. An intense damping peak is observed when the Rabi frequency Omega_R falls in the vicinity of the Larmor frequency of protons w_N, while the damping time t_R of oscillations reaches values 10 times shorter than the phase coherence time t_2 measured at the same temperature. The experiments are interpreted by the N-spin model showing that t_R is directly associated with the decoherence via electronic/nuclear spin cross-relaxation in the rotating reference frame. It is shown that this decoherence is accompanied with energy dissipation in the range of the Rabi frequencies w_N - sigma_e < Omega_R < w_N, where sigma_e is the mean super-hyperfine field (in frequency units) induced by protons at SMMs. Weaker damping without dissipation takes place outside this dissipation window. Simple local field estimations suggest that this rapid cross-relaxation in resonant microwave field observed for the first time in SMMV_15 should take place in other SMMs like Fe_8 and Mn_12 containing protons, too.
@article{arxiv.1006.4960,
title = {Decoherence window and electron-nuclear cross-relaxation in the molecular magnet V 15},
author = {J. H. Shim and S. Bertaina and S. Gambarelli and T. Mitra and A. Müller and E. I. Baibekov and B. Z. Malkin and B. Tsukerblat and Bernard Barbara},
journal= {arXiv preprint arXiv:1006.4960},
year = {2013}
}