| 1. |
- Andreeva, M. A., et al.
(författare)
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Depth selective investigations of magnetic multilayers by X-ray resonant magnetic reflectivity
- 2006
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 300:1, s. e371-e374
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Tidskriftsartikel (refereegranskat)abstract
- We have measured and analyzed the X-ray resonant Bragg reflectivity spectra from BCC [Fe/Co]n superstructure near the L2,3 absorption edges of iron. The developed general computer code for the reflectivity calculations from arbitrary anisotropic multilayers allows us to test the different approaches to the treatment of the Bragg reflectivity spectra. We have proved that the observed asymmetry of the spectrum shape at the first-order Bragg peak for the right and left circular polarizations is predominantly caused by the magnetization of the central part of iron layers. The influence of interfaces is almost negligible. The fit of the energy dependence of the integral intensity of the Bragg reflection for the [Fe6/Co6]50 sample gives the value of the magnetic moment of Fe atoms in the central parts of Fe layers ∼2.6 μB, that is larger than the volume value.
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| 2. |
- Andreeva, M. A., et al.
(författare)
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Magnetic ordering in a [Fe/Co](35) BCC film studied by nuclear resonant reflectometry
- 2007
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 104:4, s. 577-585
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of the angular dependences of nuclear resonant reflectivity time spectra for different models of magnetic ordering in films reveals an ambiguity in the magnetization direction determined from spectra measured at one orientation of the sample. This analysis explains features in the spectra of the nuclear resonant reflectivity from a MgO/[Fe(6 ML)/Co(3 ML)]35/V (1 nm) film measured before and after sample rotation by 90° about the normal to the surface. It is shown that the spectrum measured only at one orientation of the sample determines only the effective azimuth angle of magnetization γeff. This does not exclude the occurrence of a domain structure, while the angle γeff does not correspond to the true direction of the preferred orientation of magnetization. The results of measurements at two orientations of the sample can be satisfactorily matched using a model that considers a coherent mixture of states with magnetization directed along the 〈110〉 axis (77%) and with a chaotic orientation of the magnetic hyperfine field B hf in the film plane for the other nuclei.
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| 3. |
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| 4. |
- Andreeva, M. A., et al.
(författare)
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Nuclear resonant reflectivity with standing waves for the investigation of a thin 57Fe layer buried inside a superconducting Si/[Mo/Si]45/57Fe/Nb multilayer
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 266:1, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- A special multilayer sample Si/[Mo/Si]45/57Fe/Nb has been prepared for the depth selective investigations of the hyperfine fields in thin iron layer at low temperatures above and below the superconducting transition in the top Nb layer (Tc 8 K) by means of the nuclear resonant reflectivity with standing waves. The periodic multilayer [Mo/Si]45 below the iron layer in our sample was used as “a standing wave generator”. A weak magnetic hyperfine splitting in the 57Fe layer was detected just at low temperature. A slight variation of the nuclear resonant reflectivity time spectra measured above and below Tc was observed. At first it was supposed that this change of the spectrum shape is caused by the spatial modulation of ferromagnetic domains in the 57Fe layer caused by a proximity effect. A closer analysis, however, reveals that the spectrum variations are due to just the changes of the relative weights of the magnetic and paramagnetic phases in 57Fe layer.
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| 5. |
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| 6. |
- Andreeva, M. A., et al.
(författare)
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Polarization selection in Mössbauer reflectivity for magnetic multilayer investigation
- 2019
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Ingår i: VII Euro-Asian Symposium on Trends In Magnetism. - : IOP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Mossbauer reflectivity experiment with polarization selection are reported. The use of the LiF polarization analyzer allows us to get the pi ->sigma' peak on the reflectivity curve at the critical angle and Mossbauer pi ->sigma' reflectivity spectra of reasonable quality at the critical angle and also at the Bragg angles of superlattice. The impressive difference of the reflectivity spectra measured near the critical angle with and without polarizations analysis is observed for [Fe-57(10)/V-10](20) multilayer characterizing by the ferromagnetic interlayer coupling. The combined fit of the whole set of spectra measured at different angles reveals the existence of antiferromagnetic Fe oxide phases in the top three bilayers. The experiment demonstrates benefits of the Mossbauer reflectivity with polarization analysis in ultrathin surface layer investigations.
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| 7. |
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| 8. |
- Baulin, R. A., et al.
(författare)
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Unique surface sensitivity to ferro- and antiferromagnetic phases by polarization analysis in synchrotron Mossbauer reflectivity
- 2021
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Ingår i: SURFACES AND INTERFACES. - : Elsevier. - 2468-0230. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- Polarization analysis of the reflected radiation has been performed in Mossbauer reflectivity measurements with a Synchrotron Mossbauer Source (SMS). Effective pi ->sigma' polarization selection is attained with LiF crystal ((6 2 2) 90 degrees-reflection for 14.4 keV radiation, angular acceptance similar to 100 '') capable of high pi ->pi' suppression. Basic features of the reflectivity with the rotated pi ->sigma' polarization are revealed in the experiment with the [Fe-57(10 ML)/V(20 ML)](20) multilayer. Selection of pi ->sigma' polarization component in Mossbauer reflectivity allows to exclude nonresonant electronic scattering, besides Mossbauer pi ->sigma' reflectivity spectra (R-spectra) contain only contributions from magnetized along the beam ferromagnetic phases. The antiferromagnetic iron oxides do not contribute to pi ->sigma' R-spectra (dichroic component is compensated). Therefore, in the Mossbauer reflectivity experiment supplemented by polarization analysis the data interpretation becomes more certain and gives information about depth position for ferromagnetic layers selectively. With this new technique we locate antiferromagnetic iron phases in the very top layer of [Fe-57(10 ML)/V(20 ML)](20) multilayer and ascertain the ferromagnetic ordered iron layers in the remaining part of the structure. This new approach in Mossbauer reflectivity has interesting perspectives for investigations of hyperfine interactions for iron complexes on the surface, ultrathin layers and multilayers with complicated magnetic structures.
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| 9. |
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