Reentrant resistance via spin-polarized quasiparticle self injection in CMR/HTSC heterostructures

Epitaxial superlattices of half-metal, colossal magnetoresistive La2/3Ca1/3MnO3 (HM-CMR) and high-Tc superconducting YBa2Cu3O7-δ (HTSC) are grown with thick and thin modulation lengths (Λ) of YBCO/LCMO, with Λ = 280 nm and 12.5 nm; respectively, on SrTiO3 (0 0 1) single-crystalline substrates by pulsed laser deposition. Transport measurements R(T) show a resistive state below T = 35 K although the superconducting transition temperature is found to be Tc = 60 K and 63 K for both different superlattices, respectively. The onset of the resistive state coincides with a magnetic transition of the samples. This can be explained by a diffusion of spin-polarized quasiparticles into the superconducting film. Which can be considered as evidence for inverse-proximity effects over a wide temperature range in HM-CMR/HTSC heterostructures.