Long-range proximity effect in Nb-based heterostructures induced by a magnetically inhomogeneous permalloy layer

• Published in: New journal of physics Vol. 19; no. 2; pp. 23037 - 23045
• Main Authors: Cirillo, C, Voltan, S, Ilyina, E A, Hernández, J M, García-Santiago, A, Aarts, J, Attanasio, C
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 20-02-2017
• Subjects: Cooper pairs; dimensional crossover; Ferromagnetism; Ferrous alloys; Heterostructures; Inhomogeneity; Magnetic alloys; Magnetism; Nickel; Niobium; Physics; proximity effect; Proximity effect (electricity); superconductivity; Thickness
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/aa5de8

Odd-frequency triplet Cooper pairs are believed to be the carriers of long-range superconducting correlations in ferromagnets. Such triplet pairs are generated by an inhomogeneous magnetism at the interface between a superconductor (S) and a ferromagnet (F). So far, reproducible long-range effects were reported only in complex layered structures designed to provide the magnetic inhomogeneity. Here we show that spin triplet pair formation can be found in simple unstructured Nb/permalloy ( Py = Ni 0.8 Fe 0.2 )/Nb trilayers and Nb/Py bilayers, but only when the thickness of the ferromagnetic layer ranges between 140 and 250 nm. The effect is related to the emergence of an intrinsically inhomogeneous magnetic state, which is a precursor of the well-known stripe regime in Py that in our samples sets in at thickness larger than 300 nm.