Ferromagnetic/superconducting bilayer structure: A model system for spin diffusion length estimation

Abstract

We report detailed studies on ferromagnet--superconductor bilayer structures. Epitaxial bilayer structures of half metal--colossal magnetoresistive La${}_{2/3}$Ca${}_{1/3}$MnO${}_3$ (HM--CMR) and high--$T_{\mathrm{c}}$ superconducting YBa${}_2$Cu${}_3$O${}_{7-\delta }$(HTSC) are grown on SrTiO${}_3$ (100) single--crystalline substrates using pulsed laser deposition. Magnetization $M$(T) measurements show the coexistence of ferromagnetism and superconductivity in these structures at low temperatures. Using the HM--CMR layer as an electrode for spin polarized electrons, we discuss the role of spin polarized self injection into the HTSC layer. The experimental results are in good agreement with a presented theoretical estimation, where the spin diffusion length ${\xi }_{\mathrm{FM}}$ is found to be in the range of ${\xi }_{\mathrm{FM}}\approx$ 10 nm.

6 pages, 7 figures, Accepted for publication in Phys. Rev. B