Phonon Bottleneck Effect Leads to Observation of Quantum Tunneling of the Magnetization and Butterfly Hysteresis Loops in (Et4N)3Fe2F9

Abstract

A detailed investigation of the unusual dynamics of the magnetization of (Et4N)3Fe2F9 (Fe2), containing isolated [Fe2F9]3- dimers, is presented and discussed. Fe2 possesses an S=5 ground state with an energy barrier of 2.40 K due to an axial anisotropy. Poor thermal contact between sample and bath leads to a phonon bottleneck situation, giving rise to butterfly-shaped hysteresis loops below 5 K concomitant with slow decay of the magnetization for magnetic fields Hz applied along the Fe--Fe axis. The butterfly curves are reproduced using a microscopic model based on the interaction of the spins with resonant phonons. The phonon bottleneck allows for the observation of resonant quantum tunneling of the magnetization at 1.8 K, far above the blocking temperature for spin-phonon relaxation. The latter relaxation is probed by AC magnetic susceptibility experiments at various temperatures and bias fields. At H=0, no out-of-phase signal is detected, indicating that at T smaller than 1.8 K Fe2 does not behave as a single-molecule magnet. At 1 kG, relaxation is observed, occurring over the barrier of the thermally accessible S=4 first excited state that forms a combined system with the S=5 state.

arXiv comment10 pages, 10 figures

References in corpus (8)

• Quantum Computing in Molecular Magnets
• Butterfly hysteresis loop and dissipative spin reversal in the S=1/2, V15 molecular complex
• Spin Tunneling and Phonon-assisted Relaxation in Mn12-acetate
• Adiabatic Landau-Zener-Stückelberg transition with or without dissipation in low spin molecular system V15
• Quantum information processing with large nuclear spins in GaAs semiconductors
• Incoherent Zener tunneling and its application to molecular magnets
• Butterfly hysteresis loop at non-zero bias field in antiferromagnetic molecular rings: cooling by adiabatic magnetization
• Butterfly Hysteresis and Slow Relaxation of the Magnetization in (Et4N)3Fe2F9: Manifestations of a Single-Molecule Magnet

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