A Caveat for Single-Molecule Magnetism: Non-linear Arrhenius Plots

TL;DR

This paper highlights the complexity of magnetization relaxation in Mn12 single-molecule magnets, showing that traditional Arrhenius plots are insufficient and proposing a modified equation for more accurate barrier estimation.

Contribution

It introduces a modified Arrhenius equation to better estimate the relaxation barrier in SMMs, accounting for multiple relaxation pathways.

Findings

Standard Arrhenius plots are inadequate for Mn12 SMMs.

Relaxation involves excited states with higher barriers and faster attempt rates.

Modified Arrhenius equation improves barrier estimation.

Abstract

The magnetization relaxation of Mn12 single-molecule magnets (SMMs) does not follow a simple Arrhenius law, even for data collected at low frequencies (5-1500 Hz) due to contributions from relaxation pathways via excited states with larger thermal barriers, but much faster attempt rates. A modified Arrhenius equation is presented as a means to overcome this problem and obtain a more reliable limiting value for the barrier to magnetization relaxation associated with the ground S=10 state.