RESUMEN
We have studied the dependence of the superconducting (SC) transition temperature on the mutual orientation of magnetizations of Fe1 and Fe2 layers in the spin valve system CoO(x)/Fe1/Cu/Fe2/Pb. We find that this dependence is nonmonotonic when passing from the parallel to the antiparallel case and reveals a distinct minimum near the orthogonal configuration. The analysis of the data in the framework of the SC triplet spin valve theory gives direct evidence for the long-range triplet superconductivity arising due to noncollinearity of the two magnetizations.
RESUMEN
Superconductor-ferromagnet (S/F) spin valve effect theories based on the S/F proximity phenomenon assume that the superconducting transition temperature Tc of F1/F2/S or F1/S/F2 trilayers for parallel magnetizations of the F1 and F2 layers (T(c)(P)) are smaller than for the antiparallel orientations (T(c)(AP)). Here, we report for CoOx/Fe1/Cu/Fe2/In multilayers with varying Fe2-layer thickness the sign-changing oscillating behavior of the spin valve effect ΔT(c) = T(c)(AP) - T(c)(P). We observe the full direct effect with T(c)(AP) > T(c)(P) for Fe2-layer thickness d(Fe2) < 1 nm and the full inverse (T(c)(AP) < T(c((P)) effect for d(Fe2) ≥ 1 nm. Interference of Cooper pair wave functions reflected from both surfaces of the Fe2 layer appear as the most probable reason for the observed behavior of ΔT(c).
RESUMEN
We have studied the nuclear magnetic resonance (NMR) of 51V nuclei in the superconductor/ferromagnet thin film heterostructures Pd_{1-x}Fe_{x}/V/Pd_{1-x}Fe_{x} and Ni/V/Ni in the normal and superconducting state. Whereas the position and shape of the NMR line in the normal state for the trilayers is identical to that observed in a single V layer, in the superconducting state the line shape definitely changes, developing a systematic distortion of the high-field wing of the resonance line. We consider this as the first experimental evidence for the penetration of ferromagnetism into the superconducting layer, a phenomenon which has been theoretically predicted recently and dubbed the spin screening effect.
RESUMEN
We studied superconducting V layers deposited on an antiferromagnetically coupled [Fe(2)V(11)](20) superlattice. The parallel upper critical magnetic field exhibits an anomalous T dependence up to the ferromagnetic saturation field of the superlattice, indicating that the superconducting transition temperature T(S) decreases when rotating the relative sublattice magnetization directions of the superlattice from antiparallel to parallel. This proves that the pair breaking effect of a Fe2 layer is reduced if at a distance of 1.5 nm a second Fe2 layer with antiparallel spin orientation exists.