Self-injection length of polarized spins in La(0.7)Ca(0.3)MnO(3)-YBa(2)Cu(3)O(7-delta) ferromagnet-superconductor heterostructures

Abstract

Studies on the self-injection length of polarized spins in La(0.7)Ca(0.3)MnO(3) (LCMO)-YBa(2)Cu(3)O(7-delta) (YBCO) heterostructures on LaAlO(3) (LAO) substrates fabricated in situ with pulsed laser deposition have been carried out. The measured critical current density, J(c) of YBCO microbridges on LAO (control) arm was found to be larger than that of the microbridges on the LCMO arm. The difference in J(c) in the two arms indicates that a certain thickness of YBCO has become effectively normal due to self-injection of spin-polarized carriers. Further, by measuring transition temperature T(c) of YBCO layers with ac susceptibility, it has been found that the thickness of the non-superconducting YBCO layer, due to self-injection at the interface, depends upon the LCMO thickness. Both the above experiments led us to estimate the maximum thickness of the non-superconducting YBCO layer at the interface due to self-injection of spin polarized quasi-particles from YBCO into LCMO; this thickness is found to be in the range 650-850 Angstrom for LCMO thickness greater than or equal to 1000 Angstrom. A control experiment performed on YBCO-LNO (LaNiO(3)) heterostructure did not show any evidence of self-injection.