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

G. Redler, C. Lampropoulos, S. Datta, C. Koo, T. C. Stamatatos, N. E. Chakov, G. Christou, and S. Hill
Phys. Rev. B 80, 094408 – Published 16 September 2009

Abstract

High-frequency electron paramagnetic resonance (HFEPR) and alternating current (ac) susceptibility measurements are reported for a new high-symmetry Mn12 complex, [Mn12O12(O2CCH3)16(CH3OH)4]CH3OH. The results are compared to those of other high-symmetry spin S=10Mn12 single-molecule magnets (SMMs), including the original acetate, [Mn12(O2CCH3)16(H2O)4]2CH3CO2H4H2O, and the [Mn12O12(O2CCH2Br)16(H2O)4]4CH2Cl2 and [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 spectroscopic evidence suggesting that the relatively weak disorder induced by desolvation 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 no measurable reduction upon desolvation.

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  • Received 5 May 2009

DOI:https://doi.org/10.1103/PhysRevB.80.094408

©2009 American Physical Society

Authors & Affiliations

G. Redler1, C. Lampropoulos2, S. Datta1, C. Koo1, T. C. Stamatatos2, N. E. Chakov2, G. Christou2, and S. Hill1,3,*

  • 1Department of Physics, University of Florida, Gainesville, Florida 32611, USA
  • 2Department of Chemistry, University of Florida, Gainesville, Florida 32611, USA
  • 3National High Magnetic Field Laboratory and Department of Physics, Florida State University, Tallahassee, Florida 32310, USA

  • *shill@magnet.fsu.edu

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Vol. 80, Iss. 9 — 1 September 2009

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