All-oxide inverse superconducting spin switch

In proximity coupled ferromagnet/superconductor/ferromagnet (F/S/F) structures the critical temperature is modulated by the relative orientation of the magnetization in the F layers (superconducting spin switch- SSS-). A larger T$_{c}$ with antiparallel (AP) compared to parallel (P) magnetizations results from the averaging of the exchange field over the coherent volume. Recent reports have shown an SSS behavior in F/S/F structures with strong ferromagnets, where superconductivity is favored for P orientation of the adjacent magnetizations. Its origin is a subject of debate. While some reports suggest enhanced pair breaking by spin-polarized quasiparticles in the AP configurations, others emphasize the effect of stray fields in depressing the superconductivity. Comparing data of bilayers and trilayers, we show that the SSS effect of our epitaxial LCMO/YBCO/LCMO structures is governed by spin transport with limited influence of stray fields.