POSTER: Transient magnetic domain wall AC dynamics studied by MOKE imaging

QUINTEROS, C. P.; GEORGE, J.-M.; CAPELUTO, M. G.; M. GRANADA; J. CURIALE; G. PASQUINI; P. DOMENICHINI; COLLIN, S.; S. BUSTINGORRY

Buenos Aires

Conferencia; Statphys 2019; 2019

IUPAP

Beside practical applications, the understanding of the magnetic domain walls (DMs) dynamics is also relevant on a wider context. From a basic point of view, DWs can be described within the general class of disordered elastic systems [Nattermann et al., PRB 42, 8577, 1990; Kolton et al., PRL 97, 057001, 2006.]. A large amount of work during the last decades has been devoted to understanding the relationship between the different dynamic regimes and the morphology and spatial correlation lengths in these systems [Jeudy et al., PRL 117, 057201, 2016; Ferre et al., C. R. Physique 14, 651, 2013; Caballero et al., PRE 97, 062122 ,2018]. However, there are still many unanswered questions. In particular, the AC dynamics of driven DWs has not been extensively explored up to now. In fact, the response to alternating magnetic fields has only been explored in limited cases and analyzed in terms of the constant field solution. Here we present recent results [Domenichini et al., submitted to PRB. arXiv?, 2019:], where we unveil phenomena in the evolution of magnetic domain walls under the application of alternating magnetic fields within the creep regime, well beyond a small fluctuation limit of the domain wall position. Magnetic field pulses were applied in ultra-thin ferromagnetic films with perpendicularanisotropy, and the resulting domain wall evolution was characterized by polar magneto-opticalKerr effect microscopy. Whereas the DC characterization is well predicted by the elastic interface model, striking unexpected features are observed under the application of alternating square pulses: magneto-optical images show that after a transient number of cycles, domain walls evolve toward strongly distorted shapes concomitantly with a modification of domain area. The morphology of domain walls is characterized with a roughness exponent when possible and contrasted with alternative observables which result to be more suitable for the characterization of this transient evolution. The final stationary convergence as well as the underlying physics is discussed.