Facultat de Física

Departament de Física de la Matèria Condensada

Magnetic-domain-wall AC dynamics in ultrathin ferromagnetic films

Gabriela Pasquini (pasquini@df.uba.ar)

Departamento de Física, FCEN, Universidad de Buenos Aires, and IFIBA, CONICET Universidad de Buenos Aires, Buenos Aires, Argentina

Magnetic domain walls (DWs) in thin films are paradigmatic examples of elastic interfaces in disordered media. In this framework, the dynamics of DWs driven by external magnetic fields reveal a complex behavior where sample disorder plays a key role. Furthermore, the response to alternating magnetic fields was scarcely explored until ecently and had been generally analyzed in terms of constant field solution acting in flat interfaces. In this talk, after an overall introduction, I present results obtained by magneto-optical imaging 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 roughness domain wall increase, with further evolution to strongly distorted shapes. We propose an analytical model [2], based on the curvature induced symmetry breaking, able to quantitatively explain the intriguing “rectification effect”. Numerical simulations, which successfully reproduce the experimental observations, support the model. I also discuss further characterization of large- and small-scale DW deformations, which may be useful in the broader context of elastic interfaces [3] and approaches.
References [1] P. Domenichini, C. P. Quinteros, M. Granada, S. Collin, J.-M. George, J. Curiale, S. Bustingorry, M. G. Capeluto, and G. Pasquini, Phys. Rev. B 99, 214401 (2019). [2] P. Domenichini, F. Paris, M. G. Capeluto, M. Granada, J.-M. George, G. Pasquini and A. B. Kolton, Phys. Rev. B 103, L220409 (2021). [3] P. Domenichini, G. Pasquini and M. G. Capeluto, Phys. Rev. B 108, 224434 (2023).