"This proposal is dedicated to hybrid systems combining High-Tc superconductors (HTCS) with (oxide or not) ferromagnets (FM). This project aims at experimentally underpinning the microscopic mechanisms of interaction between HTCS and FM. Our goals are to understand how the d-wave superconductivity of HTCS diffuses into a FM material (in particular to determine if new quantum states such as spin-triplet pairing emerge in the FM), and to characterize spin-polarized quasiparticle transport across HTCS/FM interfaces (to measure the spin diffusion length, and to determine the mechanisms of spin relaxation in HTCS). These objectives are key to understand novel behaviours observed in HCTS/FM hybrids. Aside from the fundamental interest of these issues, the possibility of coupling HTCS across FMs over long distances, and the way the phase of the superconducting wave function evolves as it travels through it, are relevant in view of the realization of HTCS magnetic Josephson junctions and related devices. On the other hand, learning about the effects of spin accumulation and the mechanism of spin diffusion in HTCS may allow enhancing “superconducting spin-switch” effects and help engineering novel magnetoresistive devices based on spin dependent transport in HTCS. This project will be developed at the hosting institution, the Unité Mixte de Physique CNRS/Thales which provides with an ideal environment, owing to the gathering of expertises available: know-how on the growth of oxide heterostructures, state-of-art nanolithography and cutting-edge close-field microscopy techniques."