Observation of a Distribution of Internal Transverse Magnetic Fields in a Mn12-Based Single Molecule Magnet

TL;DR

This study observes a distribution of internal transverse magnetic fields in a Mn12-based single molecule magnet, explaining key quantum tunneling behaviors through a model of tilted molecular easy axes.

Contribution

It introduces a model attributing the transverse field distribution to tilts in molecular easy axes, advancing understanding of quantum tunneling in SMMs.

Findings

Distribution of transverse fields affects tunneling rates

Magnetic relaxation shows a hole in the field distribution

Tunneling features explained by easy axis tilts

Abstract

A distribution of internal transverse magnetic fields has been observed in single molecule magnet (SMM) Mn12-BrAc in the pure magnetic quantum tunneling (MQT) regime. Magnetic relaxation experiments at 0.4 K are used to produce a hole in the distribution of transverse fields whose angle and depth depend on the orientation and amplitude of an applied transverse ``digging field.'' The presence of such transverse magnetic fields can explain the main features of resonant MQT in this material, including the tunneling rates, the form of the relaxation and the absence of tunneling selection rules. We propose a model in which the transverse fields originate from a distribution of tilts of the molecular magnetic easy axes.