Experimental observation of guided polarized neutrons in magnetic-thin-film waveguides

Pogossian, S. P.; Menelle, A.; Gall, H. Le; Desvignes, J.M.; Artinian, M.

doi:10.1103/physrevb.53.14359

Cited by 24 publications

(24 citation statements)

References 16 publications

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“…The theory of neutron channeling was developed in [16]. Experimentally, the phenomenon of neutron channeling was observed in [8,17,18] and the channelling length was measured experimentally in [19,20]. It has also been demonstrated that it may be used for production of unpolarised [21] and polarised [22,23] neutron microbeams, which was used for the investigation of amorphous magnetic wires [24,25].…”

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confidence: 99%

Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

et al. 2016

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We present and apply a new method to measure directly weak magnetization in thin films. The polarization of a neutron beam channeling through a thin film structure is measured after exiting the structure edge as a microbeam. We have applied the method to a tri-layer thin film structure acting as a planar waveguide for polarized neutrons. The middle guiding layer is a rare earth based ferrimagnetic material TbCo5 with a low magnetization of about 20 mT. We demonstrate that the channeling method is more sensitive than the specular neutron reflection method.PACS numbers: 3.75. Be, Magnetic nanomaterials are widely used in practical applications and in fundamental physics. Therefore the development of new methods providing enhanced sensitivity for the characterization of their magnetic properties is a challenge. One of the well-established methods for magnetic thin films and nanostructures characterization is the Polarised Neutron Reflectometry (PNR) technique [1]. Its strength is the unique ability to probe the magnitude and the direction of the magnetization vector as a function of the depth in magnetic heterostructures. For collinear spin configurations, the PNR method resolves the depth dependence of the scattering length densities (SLD) ρ(z) which depends on the neutron polarization: ρ ± (z) = ρ 0 (z) ± cB(z). Here ρ 0 (z) and B(z) are the depth profiles of the nuclear SLD and the magnetic induction. By measuring reflectivities of spin-up and spin-down neutrons and fitting them to theoretical values one can extract the SLD depth profile and the depth dependence of the induction in a film. The method is routinely used for the characterization of ferromagnetic systems with rather high magnetization (about 0.3 -2 T). Being a model dependent method it leads to the nonuniqueness of the resulting set of parameters describing the system. As a result, the accuracy of the fitted parameters depends both on the adequacy of a model and on the quality of the experimental data. For systems with weak magnetization (∼ 10 mT), PNR requires very long measurement times (∼ 10 2 hours) in order to achieve sufficient statistics. This is usually not compatible with standard neutron reflectometry experiments.Weak magnetizations, typically less than 100 mT, are characteristic of ferrimagnetic materials or magnetic oxides. Magnetic materials such as Fe 3 O4, CoFe 2 O 4 , BiFeO 3 , GaFeO 3 , Bi 3 Fe 5 O 12 , NiCoMnAl are being increasingly studied because of their specific properties, either their electronic properties [2], their magneto-electric properties [3], their magneto-optical [4] or their magneto caloric properties [5]. The study of these materials is often limited by the weakness of the magnetic interfacial effects that are of interest. While XMCD [6] is a very sensitive technique to probe surface magnetism, it is sometimes rather difficult to apply to complex heterostructures as used in spintronic devices. Also, the XRMS [7] technique cannot access thicker layer structure because the soft x-ray penetration depth is on the order...

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Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

et al. 2016

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“…Neutron reflectivity curves on the films doped with benzene-d 6 were obtained on the EROS time-of-flight reflectometer (Saclay, France) described in detail elsewhere (Pogossian & Menelle, 1996). Measurements were performed on the horizontal samples at the incident angles of 1.1 0 using a beam of 1 mm in height and 20 mm in width.…”

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confidence: 99%

Small-angle X-ray scattering and neutron reflectivity studies of Langmuir–Blodgett films of copper tetra-tert-butyl-azaporphyrines

Valkova¹,

Menelle²,

Borovkov³

et al. 2003

J Appl Crystallogr

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Langmuir-Blodgett (LB) films of tetra-tert-butyl-substituted copper azaporphyrines, namely phthalocyanine (CuPc'), tetra-3-nitrophthalocyanine (CuPc*) and porphyrazine (CuPaz'), are studied by small-angle scattering technique. Two kinds of systems are under investigation: first, the CuPc'/Cd-stearate-d 35 superlattices; second, the LB films of CuPc', CuPc* and CuPaz' doped with benzene-d 6. X-ray diffraction patterns of the superlattices exhibit bilayer structural units indicating existence of not only 1D but also 3D nano-aggregates of CuPc'. The neutron reflectivity study on the films heavily doped with benzene-d 6 indicates that π-deficiency and size of the azaporphyrine nuclei favor interactions between the nano-aggregates.

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“…Additionally, in 1994, Feng et al experimentally demonstrated confined propagation of modes for slow neutrons in thin titanium films [8]. For further significant works on confined thermal neutron propagation in thin planar waveguides, also in the framework of neutron optics, see the other references in [8][9][10][11][12][13][14]. Other important studies are those of Kumakhov et al [15] and Chen et al [16], both in 1992, establishing experimentally the focusing of slow neutrons by using polycapillary glass fibre.…”

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confidence: 99%

Neutron waveguides in neutron optics: Green’s functions formalism with Dirichlet boundary conditions

Peña

Calvo

Alvarez‐Estrada

2020

Journal of Modern Optics

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In neutron optics, we analyse the propagation of slow (thermal) neutrons along a semi-infinite waveguide limited by a large repulsive potential (reminding the propagation of light along an optical fibre). We set an ideal case of a straight empty two-dimensional semi-infinite waveguide limited by an infinitely repulsive potential (Dirichlet conditions on its boundaries). The neutron wave function is given through an integral representation involving the incoming wave with energy E, Green's function and certain functions defined on the boundaries. The latter functions follow from the Dirichlet conditions, thereby proposing a new formalism in neutron optics. We develop various approximations (through Fourier and Hilbert transforms) and numerical computations. We get: (a) the expected extinction of the incoming wave for very large penetration into the waveguide, (b) the generation of propagation modes and their number for suitably large penetration, as E increases, (c) an estimate of the critical angle.

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Experimental observation of guided polarized neutrons in magnetic-thin-film waveguides

Cited by 24 publications

References 16 publications

Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films

Small-angle X-ray scattering and neutron reflectivity studies of Langmuir–Blodgett films of copper tetra-tert-butyl-azaporphyrines

Neutron waveguides in neutron optics: Green’s functions formalism with Dirichlet boundary conditions

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