Spin relaxation in -acetate
Department of Physics and Astronomy, University of Basel
Klingelbergstrasse 82, 4056 Basel, Switzerland
Accepted: 22 March 1999
We present a comprehensive theory of the magnetization relaxation in a Mn12-acetate crystal based on thermally assisted spin tunneling induced by quartic anisotropy and weak transverse magnetic fields. The overall relaxation rate as a function of the magnetic field is calculated and shown to agree well with data including all resonance peaks. The Lorentzian shape of the resonances is also in good agreement with recent data. A generalized master equation including resonances is derived and solved exactly. It is shown that many transition paths with comparable weight exist that contribute to the relaxation process. Previously unknown spin-phonon coupling constants are calculated explicitly.
PACS: 75.45.+j – Macroscopic quantum phenomena in magnetic systems / 75.50.Tt – Fine-particle systems / 75.30.Pd – Surface magnetism
© EDP Sciences, 1999