Giant transversal particle diffusion in a longitudinal magnetic ratchet

TL;DR

This paper investigates how an oscillating magnetic field dramatically enhances the transversal diffusion of paramagnetic particles on a garnet film, revealing a giant ratchet effect and its dependence on driving frequency.

Contribution

It provides the first experimental observation of giant transversal diffusion enhancement in a magnetic ratchet system and offers a theoretical explanation involving disorder effects.

Findings

Transversal diffusion coefficient increases by nearly four orders of magnitude with magnetic field.

Diffusion exhibits a pronounced maximum at a specific driving frequency.

Experimental results are explained by a model considering disorder effects in the magnetic film.

Abstract

We study the transversal motion of paramagnetic particles on a uniaxial garnet film, exhibiting a longitudinal ratchet effect in the presence of an oscillating magnetic field. Without the field, the thermal diffusion coefficient obtained by video microscopy is $D_{0}\approx 3\times 10^{-4}$ $\mu m^2/s$. With the field, the transversal diffusion exhibits a giant enhancement by almost four decades and a pronounced maximum as a function of the driving frequency. We explain the experimental findings with a theoretical interpretation in terms of random disorder effects within the magnetic film.