Tunneling Splittings in Mn12-Acetate Single Crystals

TL;DR

This study investigates quantum tunneling in Mn12-acetate crystals using a Landau-Zener multi-crossing method, revealing a distribution of tunnel splittings and the influence of disorder and dipolar interactions on magnetic relaxation.

Contribution

It introduces a novel application of the Landau-Zener multi-crossing technique to analyze tunneling splittings and their distribution in Mn12-acetate, highlighting disorder effects.

Findings

Distribution of tunnel splittings inferred from data

Inhomogeneity due to solvent disorder modeled

Dipolar interactions affect magnetic relaxation

Abstract

A Landau-Zener multi-crossing method has been used to investigate the tunnel splittings in high quality Mn$_{12}$-acetate single crystals in the pure quantum relaxation regime and for fields applied parallel to the magnetic easy axis. With this method several individual tunneling resonances have been studied over a broad range of time scales. The relaxation is found to be non-exponential and a distribution of tunnel splittings is inferred from the data. The distributions suggest that the inhomogeneity in the tunneling rates is due to disorder that produces a non-zero mean value of the average transverse anisotropy, such as in a solvent disorder model. Further, the effect of intermolecular dipolar interaction on the magnetic relaxation has been studied.