Peculiarities of neutron waveguides with thin Gd layer

We report on a study of the structural, magnetic and superconducting properties of Nb(25nm)/Gd(d f )/Nb(25nm) hybrid structures of a superconductor/ ferromagnet (S/F) type. The structural characterization of the samples, including careful determination of the layer thickness, was performed using neutron and X-ray scattering with the aid of depth sensitive mass-spectrometry. The magnetization of the samples was determined by SQUID magnetometry and polarized neutron reflectometry and the presence of magnetic ordering for all samples down to the thinnest Gd(0.8nm) layer was shown. The analysis of the neutron spin asymmetry allowed us to prove the absence of magnetically dead layers in junctions with Gd interlayer thickness larger than one monolayer. The measured dependence of the superconducting transition temperature Tc(d f ) has a damped oscillatory behavior with well defined positions of the minimum at d f =3nm and the following maximum at d f =4nm; the behavior, which is in qualitative agreement with the prior work (J.S. Jiang et al, PRB 54, 6119). The analysis of the Tc(d f ) dependence based on Usadel equations showed that the observed minimum at d f =3nm can be described by the so called "0" to "π" phase transition of highly transparent S/F interfaces with the superconducting correlation length ξ f ≈ 4nm in Gd. This penetration length is several times higher than for strong ferromagnets like Fe, Co or Ni, simplifying thus preparation of S/F structures with d f ∼ ξ f which are of topical interest in superconducting spintronics.

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“…1). The bilayer Ta/Cu on the top is required to protect against oxidation and to create a neutron waveguide structure [45].…”

Section: Sample Fabrication and Experimental Techniquesmentioning

confidence: 99%

Magnetic and superconducting phase diagram of Nb/Gd/Nb trilayers

et al. 2018

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Neutron reflectometry studies of Gd/Nb and Cu₃₀Ni₇₀/Nb superlattices

Khaydukov

Кравцов

Morari

et al. 2019

J. Phys.: Conf. Ser.

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We performed a comparative study of magnetic proximity effects in [Gd(5nm)/Nb(25nm)]12 and [Cu30Ni70(6nm)/Nb(27nm)]12 superlattices of S/F type by means of transport measurements and neutron scattering. Transport measurements have shown that Gd/Nb and CuNi/Nb superlattices shows 3D and 2D type of superconductivity respectively. In the case of proximity coupled Gd/Nb superconductor the effective thickness of the superconducting region, 300nm is enough to expel significant amount of applied magnetic field which was detected by neutron scattering. In decoupled CuNi/Nb superlattice thickness of every superconducting layer is only 27nm which is not enough to expel applied magnetic field. Our study shows how neutron reflectometry can be applied to study proximity coupling in superconducting/ferromagnet heterostructures.

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