Incommensurate Transverse Anisotropy Induced by Disorder and Spin-Orbit-Vibron Coupling in Mn12-acetate

TL;DR

This paper investigates how disorder and vibrational-electronic coupling in Mn12-acetate lead to incommensurate anisotropy axes, causing quenching of tunnel-splitting oscillations under transverse magnetic fields.

Contribution

It provides a detailed calculation of the principal axes of anisotropy induced by disorder and vibrational coupling, revealing their incommensurability and its effects.

Findings

In-plane principal axes of second-order anisotropy differ from fourth-order anisotropy axes.

Incommensurability leads to quenching of tunnel-splitting oscillations.

Vibrational-electronic coupling significantly influences magnetic anisotropy.

Abstract

It has been shown within density-functional theory that in Mn$_{12}$-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.