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(a) Optical image of the YBCO∕LSMO surface. TBs are clearly visible in three different directions. (b) Magneto-optical images of the same region of the sample taken at . Bright and dark straight lines in the magnetic patterns reveal the presence of out-of-plane structures pinned at TBs, where the magnetic moments are tilted up (bright lines—) and down (dark lines—) with respect to the film plane. Other disordered structures due to sample microdamages and to scratches are also visible. (c) Scheme displaying the ordering of the magnetic moments (arrows) in the manganite film. In-plane magnetic domains lie in between out-of-plane structures.
(a),(b) distributions measured at . (a) After zero external field cooling, DWs are still visible since they spontaneously nucleate vortices in the superconducting layer. (b) The fanlike magnetic field pattern is perturbed by DWs during vortex diffusion inside the YBCO (out-of-plane magnetic field directed upward). (c) (Inset) profiles evaluated along the dotted lines traced in Fig. (a) (open symbols) and Fig. (b) (solid symbols) crossing a couple of DWs ( and , respectively). From the flux front profile we estimated a critical current density of about .
A selected area with the fanlike flux pattern, obtained from the difference between measurements in Figs. 2(a) and 2(b). The DW blocking action is clearly visible in the fan shape flux pattern as vortex piling up at (brighter lines) and vortex annihilation at (darker lines). In the inset, a profile across a couple of DWs ( and under the dotted line in the main figure) is shown. The mean slope is due to the critical state profile.
Zoom of the distribution in the sample central part . Here vortices diffuse along DWs. As clear from the fork shape of the critical state pattern (top side), the effect of out-of-plane DWs is to block vortices of opposite polarity (black arrows) and to channel those of the same sign (white arrows). The sawtooth pattern, across the Meissner part (dark area on bottom), is the DW structure induced by the supercurrent loop inside the indicator film.
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