  We have used coherent, resonant, x-ray magnetic speckle patterns to measure
the statistical evolution of the microscopic magnetic domains in perpendicular
magnetic films as a function of the applied magnetic field. Our work
constitutes the first direct, ensemble-averaged study of microscopic magnetic
return point memory, and demonstrates the profound impact of interfacial
roughness on this phenomenon. At low fields, the microscopic magnetic domains
forget their past history with an exponential field dependence.
