Coherent forward-scattering amplitude in transmission and grazing incidence Mössbauer spectroscopy

Bottyán

Callens

et al. 2015

J Synchrotron Radiat

Self Cite

Section: Grazing Incidence Geometrymentioning

confidence: 99%

“…The index of refraction is related to the susceptibility matrix χ (Deák et al, 2001;Deák et al, 1996) through…”

Section: General Considerationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stroboscopic detection of nuclear resonance in an arbitrary scattering channel

Bottyán

Callens

et al. 2015

J Synchrotron Radiat

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“…In forward scattering geometry, Blume and Kistner [25] established, already in 1968, the theory for Mössbauer absorption of γ radiation. The theory was later extended for grazing incidence scattering on stratified media [26][27][28][29] and computer programs also became available [30][31][32][33][34]. As a result, reciprocity situations can be simulated and the condition and aspects of reciprocity can be tested.…”

mentioning

confidence: 99%

Switching Reciprocity On and Off in a Magneto-Optical X-Ray Scattering Experiment Using Nuclear Resonance ofα−Fe57Foils

Bottyán²,

Fülöp³

et al. 2012

Phys. Rev. Lett.

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Reciprocity is when the scattering amplitude of wave propagation satisfies a symmetry property, connecting a scattering process with an appropriate reversed one. We report on an experiment using nuclear resonance scattering of synchrotron radiation, which demonstrates that magnetooptical materials do not necessarily violate reciprocity. The setting enables to switch easily between reciprocity and its violation. In the latter case, the exhibited reciprocity violation is orders of magnitude larger than achieved by previous wave scattering experiments.PACS numbers: 03.65. Nk, 76.80.+y, 78.70.Ck, 78.20.Ls Keywords: reciprocity, scattering theory, nuclear resonance scattering, Mössbauer spectroscopyThe reciprocity principle, which states that the interchange of source and detector does not change the scattering amplitude of a wave scattering process, cannot be derived from first principles and is not necessarily fulfilled. The term 'reciprocity' has been introduced by Stokes [1], and the numerous subsequent related publications cover the whole 20 th century, as it is summarized in the review paper of Potton [2]. Reciprocity theorems were derived for various scattering problems, telling under which conditions and limitations the reciprocity principle is valid [3][4][5][6][7], and situations in the field of local and nonlocal electromagnetism [8][9][10][11], sound waves [12], electric circuits [13], radio communication [14], and local and nonlocal quantum mechanical scattering problems [5,15,16] were considered. Nonreciprocal devices (circulators and isolators) with on-chip integration possibility were also suggested [17]. In a recent work of Deák and Fülöp [23], a general reciprocity theorem was formulated, which covers all cases of wave phenomena that can be represented by a Schrödinger equation, with Hamiltonian H = H 0 + V , where H 0 describes free wave propagation and V the scatterer. Reciprocity is more general than time reversal invariance, can occur for absorptive scattering media as well, and it also fundamentally differs from rotational invariance [23]. We note that, in X-ray optics, the term non-reciprocity may also refer to time-reversal odd optical activity [18][19][20][21][22], which meaning differs from the historical one used here [2,23].Here, we report on an experimental investigation of reciprocity and its violation. Our aim was threefold: to show that magneto-optical materials do not necessarily violate reciprocity, to control easily whether reciprocity is present or missing, and to demonstrate that reciprocity violation can be a remarkably strong effect. The example considered belongs to the field of optics, where the multiple scattering of X-rays or neutrons can be described by an index of refraction [24]. In forward scattering geometry, Blume and Kistner [25] established, already in 1968, the theory for Mössbauer absorption of γ radiation. The theory was later extended for grazing incidence scattering on stratified media [26][27][28][29] and computer programs also became available [30][31][32][3...

Specular and Off-Specular Synchrotron M�ssbauer Reflectometry: Applications to Thin Film Magnetism

Nagy

Bottyán

et al. 2002

phys. stat. sol. (a)

Synchrotron Mö ssbauer Reflectometry (SMR) is a novel tool for studying the magnetic structure of multilayers. The orientation of the layer magnetisation in an antiferromagnetically coupled multilayer is determined from the intensity of the pure nuclear reflection in specular time-integral SMR experiments. The value of the saturation field is estimated with high accuracy. The bulk spinflop transition in an Fe/Cr superlattice of fourfold in-plane magnetocrystalline anisotropy is demonstrated. The width of the off-specular (diffuse) scattering peak is a measure of the in-plane antiferromagnetic domain size. The domain correlation length of 2.6 mm measured in remanence on the Fe/Cr superlattice following magnetic saturation is in good agreement with semi-empirical model calculations. D. L. Nagy et al.: Specular and Off-Specular Synchrotron Mö ssbauer Reflectometry Fig. 2. Normalised intensity of the AF peak of a MgO(001)/[ 57 Fe(26 A)/Cr(13 A)] 20 multilayer vs. magnetic field H perpendicular to the photon beam during bulk spin-flop. The continuous line is guiding the eyes. The inset shows the MOKE angle vs. magnetic field