Observation of resonance enhanced neutron standing waves through (n, α) reaction

Аксенов, В. Л.; Nikitenko, Yu. V.; Radu, F.; Gledenov, Yu. M.; Sedyshev, P.

doi:10.1016/s0921-4526(99)01270-3

Cited by 35 publications

(17 citation statements)

References 2 publications

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“…1a). Below the critical edge at the resonance conditions the neutron wave function density is resonantly enhanced in the channelling layer B [10] and hence all the neutron interactions such as the spin-flip cross section [11], the diffuse scattering [12,13], alpha-particles [14] or gammaquanta [15] emission.Let r BA(BC) be the complex reflection amplitudes of the tunnelling layer and of the reflector layer, from inside out. Let k B = k 2 0 − u ± µB be the normal component of neutron wave-vector in the investigated layer of thickness d. The complex reflection coefficients can be calculated numerically based on the parameters of the reflector layer, the tunnelling layer, and of the resonant layer.…”

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confidence: 99%

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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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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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confidence: 99%

“…Where r BA and r BC are the complex reflection amplitudes from the complete structures to the left and to arXiv:1511.07286v2 [cond-mat.mtrl-sci] 24 Nov 2015 [12,13], alpha-particles [14] or gamma-quanta [15] …”

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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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“…In [19] the dips on total neutron reflection and maxima of gamma-irradiation were observed for the layer Gd 2 O 3 . In [20] the resonant minima at total neutron reflection and resonant maxima of alpha-particles intensity were registered for the layer 6 LiF. The enhanced off-specular neutron scattering due to interface roughness was observed in [21,22].…”

Section: Introductionmentioning

confidence: 87%

Polarized neutron channeling in weakly magnetic films

Кожевников

Жакетов

Keller

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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We describe a new sensitive method for the investigation of weakly magnetic films placed inside a tri-layer planar waveguide. Polarized neutrons tunnel into the waveguide through the surface, channel along the layers and are emitted from the end face as a narrow and slightly divergent microbeam. Polarization analysis permits to detect very small magnetization in the order of a few 10 Gauss. The magnetic film containing the rare-earth element Tb was investigated using both fixed wavelength and time-of-flight polarized neutron reflectometers. The experimental results are presented and discussed.

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“…The difference between the NSW formed with the two polarization states was quantified via the characteristic γ fluorescence after neutron capture by Gd [69]. In another study [70], neutron resonance in a 6 LiF/Ti/Cu/glass layered structure was quantified in simultaneous measurements of neutron reflectivity and the 6 Li(n, α) 3 H nuclear reaction as fluorescence signal. The observation of the neutron density resonant character in the Ti spacer needed a neutron absorbing layer which was the 6 LiF cap layer itself.…”

Section: Thin Films On Solid Surfacesmentioning

confidence: 99%

Structural characterization of soft interfaces by standing-wave fluorescence with X-rays and neutrons

Schneck

Demé

2015

Current Opinion in Colloid & Interface Science

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We present a review of standing-wave fluorescence techniques with x-rays and neutrons for the elementspecific structural investigation of interfaces. The basic principles are introduced and typical measurement configurations with their advantages and limitations are compared. An overview of studies dealing with various types of interfaces is given. In particular, work on soft and biological matter in planar, interfacial geometries is discussed.

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Observation of resonance enhanced neutron standing waves through (n, α) reaction

Cited by 35 publications

References 2 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

Polarized neutron channeling in weakly magnetic films

Structural characterization of soft interfaces by standing-wave fluorescence with X-rays and neutrons

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