Crystal lattice desolvation effects on the magnetic quantum tunneling of single-molecule magnets

Abstract

High-frequency electron paramagnetic resonance (HFEPR) and AC susceptibility measurements are reported for a new high-symmetry Mn12 complex, [Mn12O12(O2CCH3)16(CH3OH)4].CH3OH. The results are compared with those of other high-symmetry spin S = 10 Mn12 single-molecule magnets (SMMs), including the original acetate, [Mn12(O2CCH3)16(H2O)4].2CH3CO2H.4H2O, and the [Mn12O12(O2CCH2Br)16(H2O)4].4CH2Cl2 & [Mn12O12(O2CCH2But)16(CH3OH)4].CH3OH complexes. These comparisons reveal important insights into the factors that influence the values of the effective barrier to magnetization reversal, Ueff, deduced on the basis of AC susceptibility measurements. In particular, we find that variations in Ueff can be correlated with the degree of disorder in a crystal which can be controlled by desolvating (drying) samples. This highlights the importance of careful sample handling when making measurements on SMM crystals containing volatile lattice solvents. The HFEPR data additionally provide important spectroscopic evidence suggesting that the relatively weak disorder induced by desolvation strongly influences the quantum tunneling interactions, and that it is under-barrier tunneling that is responsible for a consistent reduction in Ueff that is found upon drying samples. Meanwhile, the axial anisotropy deduced from HFEPR is found to be virtually identical for all four Mn12 complexes, with essentially no measurable reduction upon desolvation.

17 pages, 6 figures, accepted for publication in Phys. Rev. B

References in corpus (6)

• Resonant Tunneling in Truly Axial Symmetry Mn12 Single-Molecule Magnets: Sharp Crossover between Thermally Assisted and Pure Quantum Tunneling
• Quantum phase interference and spin parity in Mn12 single-molecule magnets
• A rotating cavity for high-field angle-dependent microwave spectroscopy of low-dimensional conductors and magnets
• Exchange Interactions and High-Energy Spin States in Mn_12-acetate
• Fabrication of Nano-Gapped Single-Electron Transistors for Transport Studies of Individual Single-Molecule Magnets
• Evidence for the S=9 excited state in Mn12-bromoacetate measured by electron paramagnetic resonance

Cited by in corpus (7)

• Magnetic Quantum Tunneling: Insights from Simple Molecule-Based Magnets
• On the anisotropy barrier reduction in fast relaxing Mn12 single-molecule magnets
• Magic angle effects in a trigonal Mn(III)3 cluster: deconstruction of a single-molecule magnet
• Effects of uniaxial pressure on the quantum tunneling of magnetization in a high-symmetry Mn12 single-molecule magnet
• Experimental determination of the Weiss temperature of Mn${}_{12}$-ac and Mn${}_{12}$-ac-MeOH
• Transverse Field Ising Ferromagnetism in Mn${}_{12}$-acetate-MeOH
• Quantum Fluctuations and Long-Range Order in Molecular Magnets