Collective Colloidal Transport Across Periodic Magnetic Landscapes

Abstract

Microscopic colloidal particles under external fields represent a versatile model system to investigate the fascinating dynamics of dissipative multibody systems under thermal noise with real time/space experiments. This chapter describes different advances obtained with paramagnetic colloidal microspheres driven above magnetic energy landscapes generated at the surface of uniaxial ferrite garnet films. These are thin ferromagnetic films that display extended periodic potential with a spatial periodicity on the colloidal length scale, where block walls organize into symmetric patterns consisting of stripes or bubbles. External, time-dependent magnetic fields are used to modulate the magnetic landscape produced by the stray field, generating an effective travelling wave potential which transport the particles at a constant and frequency tunable speed. In such systems, novel dynamical regimes are observed, from localized particle trajectories to directed transport, and such regimes are used to explore with single particle resolution, general physical phenomena that occurs on other condensed matter systems.