Magnetic-domain-wall AC dynamics in ultrathin ferromagnetic films

DOMENICHINI, P.; GRANADA, M.; BUSTINGORRY, S.; PASQUINI, G.; QUINTEROS, C. P.; CURIALE, J.; CAPELUTO, M. G.; PARIS, F.; GEORGE, J.-M.; KOLTON, A. B.

San Carlos de Barilche

Workshop; Spin Argentina 2022; 2022

The dynamics of domain walls (DWs) under external magnetic fields reveals a complex behavior where sample disorder plays a key role. Furthermore, the response to alternating (AC) magnetic fields has only been explored in few cases and analyzed in terms of the constant field solution acting on interfaces that are flat on average. Here we present results obtained by magneto-optical imaging of the evolution of magnetic DWs in ultrathin ferromagnetic films with perpendicular anisotropy, under the application of AC magnetic fields within the creep regime. Whereas the DC characterization is well predicted by an elastic flat interface model,unexpected features are observed under the application of alternating square pulses in bubble micrometer- sized magnetic domains [1]: We show that under a zero bias AC field there is a striking bubble area reduction, concomitant with a DW roughness increase, with further evolution to strongly distorted shapes. We propose an analytical model [2], based on the curvature induced symmetry breaking, which is able to quantitatively explain the intriguing ?rectification effect?. Numerical simulations, capable of reproducing the experimental observations, support the analytical model. A qualitative explanation of the enhancement of large scale dynamic roughening is also proposed.