Enhanced diffusion and anomalous transport of magnetic colloids driven above a two-state flashing potential

TL;DR

This study combines experiments and theory to explore how magnetic colloids move under a flashing magnetic potential, revealing normal diffusion at high amplitudes and anomalous subdiffusive behavior at lower amplitudes due to structural disorder.

Contribution

It introduces a persistent random walk model and numerical simulations to explain the origin of anomalous diffusion caused by dynamic disorder in magnetic lattices.

Findings

Normal diffusion at high driving amplitudes

Subdiffusive and oscillatory behavior at low amplitudes

Anomalous motion driven by structural disorder

Abstract

We combine experiment and theory to investigate the diffusive and subdiffusive dynamics of paramagnetic colloids driven above a two-state flashing potential. The magnetic potential was realized by periodically modulating the stray field of a magnetic bubble lattice in a uniaxial ferrite garnet film. At large amplitudes of the driving field, the dynamics of particles resembles an ordinary random walk with a frequency-dependent diffusion coefficient. However, subdiffusive and oscillatory dynamics at short time scales is observed when decreasing the amplitude. We present a persistent random walk model to elucidate the underlying mechanism of motion, and perform numerical simulations to demonstrate that the anomalous motion originates from the dynamic disorder in the structure of the magnetic lattice, induced by slightly irregular shape of bubbles.