Superconducting imprint of spin textures

Research on proximity effects in superconductor/ferromagnetic hybrids has most often focused on how superconducting properties are affected—and can be controlled—by the effects of the ferromagnet’s exchange or magnetic fringe fields. The opposite, namely the possibility to craft, tailor, and stabilize the magnetic texture in a ferromagnet by exploiting superconducting effects, has been more seldom explored. Here we show that the magnetic flux trapped in high-temperature superconducting YBa2Cu3O7-δ microstructures can be used to modify the magnetic reversal of a hard ferromagnet—a cobalt/platinum multilayer with perpendicular magnetic anisotropy—and to imprint unusual magnetic domain distributions in a controlled manner via the magnetic field history. The domain distributions imprinted in the superconducting state remain stable, in absence of an external magnetic field, even after increasing the temperature well above the superconducting critical temperature, at variance to what has been observed for soft ferromagnets with in-plane magnetic anisotropy. This opens the possibility of having non-trivial magnetic configuration textures at room temperature after being tailored below the superconducting transition temperature. The observed effects are well explained by micromagnetic simulations that demonstrate the role played by the magnetic field from the superconductor on the nucleation, propagation, and stabilization of magnetic domains.

a) Sketch of the experimental set-up. XMCD, measured as the normalized difference in absorption for incoming left and right helicity of circularly polarized radiation, is proportional to the projection of the magnetization (light red and blue arrows) along the beam propagation direction (red and blue arrows). (b) Absorption spectrum obtained at the Co L2,3-edges for (Co/Pt)5 on top (dots) and around the SC structure (line). (c,d) XAS and XMCD images obtained at Co L3-edge (777.55 eV) at 50 K after a demagnetization process at 140 K. (e) MFM phase image showing a similar magnetization pattern.

This work has been done in collaboration with the groups of J. Santamaría (GFMC, University Complutense of Madrid, Spain) and Sergio Valencia (Helmholtz-Zentrum Berlin für Materialien und Energie, Germany).

The full text can be found here.

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