Spectroscopic magnetrotransport across YBa$_{2}$Cu$_{3}$O$_{7-x}$/La$_{0.7}$Ca$_{0.3}$MnO$_{3}$ microjunctions

Superconducting/Ferromagnetic YBCO/LCMO heterostructures exhibit a number of novel behaviors, such as unexpected long-range proximity effects, and giant magnetoresistance. The microscopic mechanisms behind these effects are under debate and include, among others, different types of charge and spin transport processes across the YBCO/LCMO interface. Characterizing these and determining the electronic density of states nearby the interfaces is key to understand the nature of the S/F interactions. With this motivation, we have fabricated vertical YBCO/LCMO and YBCO/LCMO/YBCO junctions (of areas down to 8 $\mu $m$^{2})$ using optical lithography and ion etching. The current-perpendicular-to-plane differential conductance shows salient features such as i) a sizable interface resistivity $\sim $ 10$^{-3 }\Omega \cdot $cm$^{2}$, ii) a prominent zero-bias conductance peak, and iii) a symmetric series of resonances at quasiparticle sup-gap energies, reminiscent of Tomasch and McMillan-Rowell oscillations. We will discuss the origin of these behaviors and their implications in regard of proximity effects.