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Phys. Rev. B 65, 014426 (2001) [5 pages]

Effects of D-strain, g-strain, and dipolar interactions on EPR linewidths of the molecular magnets Fe8 and Mn12

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Kyungwha Park1,*, M. A. Novotny1,†, N. S. Dalal2, S. Hill3,‡, and P. A. Rikvold1,4
1School of Computational Science and Information Technology, Florida State University, Tallahassee, Florida 32306
2Department of Chemistry, Florida State University, Tallahassee, Florida 32306
3Department of Physics, Montana State University, Bozeman, Montana 59717
4Center for Materials Research and Technology and Department of Physics, Florida State University, Tallahassee, Florida 32306

Received 20 August 2001; published 11 December 2001

Electron paramagnetic resonance measurements on single crystals of the molecular magnets Fe8 and Mn12 reveal complex nonlinearities in the linewidths as functions of energy eigenstate, frequency, and temperature. Using a density-matrix equation with distributions of the uniaxial anisotropy parameter D, the Landé g factor, and dipolar interactions, we obtain linewidths in good agreement with experiments. Our study shows that the distribution in D is common to the examined molecular magnets Fe8 and Mn12 regardless of the qualities of the samples. This could provide the basis for a proposed tunneling mechanism due to lattice defects. The distribution in g is also quite significant for Mn12.

© 2001 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.65.014426
DOI:
10.1103/PhysRevB.65.014426
PACS:
75.45.+j, 75.50.Xx, 76.30.-v

*Electronic address: park@csit.fsu.edu

†Present address: Department of Physics and Astronomy, Mississippi State University, Mississippi State, MS 39762.

‡Present address: Department of Physics, University of Florida, Gainesville, FL 32611.

 
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