It has been shown within density-functional theory that in Mn12-acetate there are effects due to disorder by solvent molecules and a coupling between vibrational and electronic degrees of freedom. We calculate the in-plane principal axes of the second-order anisotropy caused by the second effect and compare them with those of the fourth-order anisotropy due to the first effect. We find that the two types of the principal axes are not commensurate with each other, which results in a complete quenching of the tunnel-splitting oscillation as a function of an applied transverse field.
@article{arxiv.cond-mat/0409206,
title = {Incommensurate Transverse Anisotropy Induced by Disorder and Spin-Orbit-Vibron Coupling in Mn12-acetate},
author = {Kyungwha Park and Mark R. Pederson and Tunna Baruah and Noam Bernstein and Jens Kortus and Steven L. Richardson and Enrique del Barco and Andrew D. Kent and Steve Hill and Naresh S. Dalal},
journal= {arXiv preprint arXiv:cond-mat/0409206},
year = {2009}
}