Exchange bias perpendicular em multicamadas de IrMn/Co/Pd

Abstract

Magnetic skyrmions are spin textures that can arise in thin films that exhibit the Dzyaloshinskii–Moriya interaction. Such interaction emerges from symmetry breaking at the interface between a ferromagnetic material and a heavy metal. Typically, skyrmions must be subjected to an external magnetic field to be stabilized, which compromises their potential for technological applications. In this work, we aimed to use the exchange bias phenomenon to replace the role of the external field in the formation of such spin textures. Thin films composed of IrMn and Co/Pd multilayers were deposited using magnetron sputtering on glass substrates. A variable-thickness Pd spacer was inserted between IrMn and the first Co layer, with the aim of gradually reducing the interaction between the antiferromagnetic and ferromagnetic layers. To induce the exchange bias phenomenon perpendicular to the film plane, the samples were subjected to heat treatments and cooled in the presence of an external magnetic field. The samples were magnetically characterized before and after treatment using AGFM and VSM techniques. Some of the as-fabricated samples exhibited perpendicular magnetic anisotropy, and after treatment, all samples showed this anisotropy. We observed a variation in the bias field and coercive field intensity with the temperature of the heat treatment and the thickness of the spacer. Magnetic force microscopy was used to observe the magnetic domain structures present in the films under three different conditions: as-fabricated samples, after magnetically saturating out-of-plane, and after an AC demagnetization protocol. Despite the presence of perpendicular anisotropy and exchange bias in most of the films, only labyrinth and bubble-type structures were observed. It was not possible to confirm the presence of skyrmions or the influence of EB on their formation.