Giant spin-phonon bottleneck effects in evaporable vanadyl-based molecules with long spin coherence

L Tesi and A Lunghi and M Atzori and E Lucaccini and L Sorace and F Totti and R Sessoli, DALTON TRANSACTIONS, 45, 16635-16643 (2016).

DOI: 10.1039/c6dt02559e

Vanadium(IV) complexes have recently shown record quantum spin coherence times that in several circumstances are limited by spin-lattice relaxation. The role of the environment and vibronic properties in the low temperature dynamics is here investigated by a comparative study of the magnetization dynamics as a function of crystallite size and the steric hindrance of the beta-diketonate ligands in VO(acac)(2) (1), VO(dpm)(2) (2) and VO(dbm)(2) (3) evaporable complexes (acac(-) = acetylacetonate, dpm(-) = dipivaloylmethanate, and dbm(-) = dibenzoylmethanate). A pronounced crystallite size dependence of the relaxation time is observed at unusually high temperatures (up to 40 K), which is associated with a giant spin-phonon bottleneck effect. We model this behaviour by an ad hoc force field approach derived from density functional theory calculations, which evidences a correlation of the intensity of the phenomenon with ligand dimensions and the unit cell size.

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