Effects of alternating forces in domain wall roughness

With a Ginzburg-Landau model that can be reduced to the quenched Edwards-Wilkinson equation, I show how it is possible to numerically emulate an experimental protocol used to probe the effects of alternating magnetic fields in ferromagnetic domains. The model allows me to capture the main experimental results: under constant field pulses only favoring domain growth or shrink, the domain wall roughness exhibits a power-law behavior described by the Kardar-Parisi-Zhang (KPZ) exponent. When instead domain walls are subjected to alternating fields favoring domain growth and shrink subsequently, the exponent in the roughness is increased. I explain this effect by arguing that under alternating fields the disorder correlation length felt by the domain wall is increased, thus pushing the region in which the KPZ exponent is observed towards larger scales. When the disorder correlation length is increased, one has access to an intermediate excess power-law with exponent 0.9 that emerges as a consequence of the microscopic interplay between disorder and thermal effects.