Extracting Stray Magnetic Fields from Thin Ferromagnetic Layers in Hybrid Superconducting/Ferromagnetic Heterostructures

• Published in: Journal of superconductivity and novel magnetism 2021-12, Vol.34 (12), p.3115-3124
• Main Authors: Paschoa, Anderson, Gonzalez, Jorge L., Nascimento, Valberto P., Passamani, Edson C.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Magnetic Materials; Magnetism; Original Paper; Physics; Physics and Astronomy; Strongly Correlated Systems; Superconductivity
• ISSN: 1557-1939; 1557-1947
• DOI: 10.1007/s10948-021-06052-0

Hybrid Nb(20)/Cu(5)/Py(2), Nb(20)/Cu(5)/Co(40) and Nb(20)/Cu(d Cu )/Py(2)/Cu(5)/Co(40) heterostructures (values in nanometers and d Cu = 0, 2.5 and 5.0) were fabricated using a confocal DC magnetron sputtering setup. Performing magnetotransport measurements and using the anisotropic Ginzburg–Landau approach, the stray field values in zero-applied field ( B 0 Co , B 0 Py and B 0 Py + Co ) were estimated as being - 9 mT ( + 31 mT) for the hybrid Nb/Cu/Co (Nb/Cu/Py) trilayers and + 36 mT for the hybrid ordinary Nb/Cu(5)/Py/Cu/Co spin-valve heterostructure. The effective fields acting on the superconducting layer in the hybrid non-ordinary Nb/Cu/Py and Nb/Cu/Co spin-valve heterostructures and its dependence with the applied magnetic field were also quantified, showing that the stray fields of thin ferromagnetic layers are the same order of magnetide but with different strengths. For an applied field of 1 T, the spin-valve effect values of - 230 mK ( + 300 mK), previously found for the hybrid Nb/Cu/Co (Nb/Cu/Py) trilayers and + 140 mK for the Nb/Cu(5)/Py/Cu/Co heterostructure, had their physical origin better discussed and demonstrated. The 2-nm-thick ferromagnetic Py layer strongly contributes to the effective fields, and the low spin-valve effect of + 140 mK for the ordinary Nb/Cu(5)/Py/Cu/Co spin-valve heterostructure would be a consequence of two contributions of opposite signs governed by the Py and Co layers and also due to the proximity effect contribution.