Studies on the self-injection length of polarized spins in La0.7Ca0.3MnO3
(LCMO)-YBa2Cu3O7-d (YBCO)
heterostructures on LaAlO3 (LAO) substrates fabricated in situ with pulsed laser deposition
have been carried out. The measured critical current density, Jc
of YBCO microbridges on LAO (control) arm was found to be larger than that of
the microbridges on the LCMO arm. The difference in Jc 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 Tc 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 Å for
LCMO thickness ≥
1000 Å. A control experiment performed on YBCO-LNO (LaNiO3)
heterostructure did not show any evidence of self-injection.
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