Non-exponential relaxation and quantum tunnel splitting in molecular magnet Fe8

TL;DR

This paper investigates magnetic relaxation in Fe8 molecular magnets, revealing non-exponential behavior caused by local stray fields, and proposes revisions to the Landau-Zener model to accurately determine tunneling splitting.

Contribution

It introduces a model accounting for local stray fields, showing their impact on relaxation dynamics and providing a method to extract tunneling splitting from experimental data.

Findings

Relaxation deviates from exponential law due to stray fields

Distribution of relaxation rates affects tunneling analysis

Revised Landau-Zener approach yields accurate tunneling splitting

Abstract

Magnetic relaxation in molecular magnets under a sweeping field is studied by taking into account local stray fields. It is found that the randomness of local stray field leads to a distribution of the relaxation rate which subsequently makes the relaxation deviate from the exponential law as predicted by the Landau-Zener model such that the Landau-Zener method needs to be revised to deduce an exact tunneling splitting. The tunneling splitting and distribution width of local stray fields are derived from the experimental data for molecular magnets Fe8.