Experimental Estimates of Dephasing Time in Molecular Magnets

TL;DR

This study uses muon spin relaxation to measure the dephasing time in isotropic molecular magnets, revealing a nuclear-origin stochastic field with a consistent dephasing time around 10 nanoseconds across different spins.

Contribution

It provides the first experimental estimate of the dephasing time in isotropic molecular magnets and suggests a nuclear origin, proposing the need for a stochastic Landau-Zener theory.

Findings

Dephasing time $ au_$ ~ 10 ns, independent of spin and ligand.

Dephasing is of nuclear origin, related to environmental stochastic fields.

Dephasing time is shorter than Zener and tunneling times in anisotropic magnets.

Abstract

Muon spin relaxation measurements in isotropic molecular magnets (MM) with a spin value S ranging from 7/2 to 27/2 are used to determine the magnitude and origin of dephasing time $\tau_\phi$ of molecular magnets. It is found that $\tau_\phi$ ~ 10 nsec with no S or ligand dependence. This indicates a nuclear origin for the stochastic field. Since $\tau_\phi$ is a property of the environment, we argue that it is a number common to similar types of MM. Therefore, $\tau_\phi$ is shorter than the Zener and tunneling times of anisotropic MM such as Fe8 or Mn4 for standard laboratory sweep rates. Our findings call for a stochastic Landau-Zener theory in this particular case.