Anomalous magnetization dynamics in artificial spin ice*

Modern nanotechnology permits one to mimic bulk spin ice crystals with ordered arrays of ferromagnetic nano-islands, which constitute a method for designing fully controlled model systems for studies of frustrated magnetic interactions in two dimensions. Thermal fluctuations within a highly degenerate ground state excite topological magnetic charges, but the nature of the field-dependent equilibrium states and their magnetic dynamics has remained elusive. Here we present results of time dependent, coherent speckle intensity and X-ray correlation spectroscopy (XPCS) in a diffraction geometry, which yields information concerning the dynamics of emergent topological charge defects in a square artificial spin ice.