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Phys. Rev. Lett. 87, 227205 (2001) [4 pages]

Distribution of Tunnel Splittings in Mn12 Acetate

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K. M. Mertes, Yoko Suzuki, and M. P. Sarachik
Physics Department, City College of the City University of New York, New York, New York 10031

Y. Paltiel, H. Shtrikman, and E. Zeldov
Department of Condensed Matter Physics, The Weizmann Institute of Science, Rehovot 76100, Israel

E. Rumberger and D. N. Hendrickson
Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093

G. Christou
Department of Chemistry, Indiana University, Bloomington, Indiana 47405

Received 28 June 2001; published 12 November 2001

In magnetic fields applied parallel to the anisotropy axis, the relaxation of the magnetization of Mn12-acetate measured for different sweep rates collapses onto a single scaled curve. The form of the scaling implies that the dominant symmetry-breaking process responsible for tunneling is a locally varying second-order transverse anisotropy, forbidden by tetragonal symmetry in the perfect crystal, which gives rise to a broad distribution of tunnel splittings in a real crystal of Mn12 acetate. Different forms applied to even- and odd-numbered steps provide a clear distinction between even resonances (associated with crystal anisotropy) and odd resonances (which require a transverse magnetic field).

© 2001 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.87.227205
DOI:
10.1103/PhysRevLett.87.227205
PACS:
75.45.+j, 75.50.Xx
 
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