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Mössbauer study of the Fe1-xNix Invar alloys by monochromatic circularly polarized source

100%

Satuła D. , Szymański K. , Dobrzyński L. , Rećko K. , Waliszewski J.

tom Vol. 48,suppl.1

71-74

X-ray diffraction measurements and Mössbauer spectroscopy with and without external magnetic field parallel to beam direction have been performed for Fe1-xNix (x = 0.25, 0.30, 0.35) alloys. The compositions of the studied alloys were chosen in order to cover the concentration range where the fcc - bcc structural transformation appears, as well as where single phase fcc Fe-Ni alloys exhibit the Invar phenomena. Spatial distribution of the iron magnetic moments is discussed. The hyperfine magnetic field (h.m.f.) distribution is analyzed within a scope of two models discussed in the literature. In the first model it is assumed that any hyperfine magnetic filed vector have the same spatial distribution (the same values of (). In the second, the low field component of the hyperfine magnetic field is ordered antiferomagnetically (or disordered) while the high field component is aligned by an external magnetic field. In order to determine the mean values of cosine of the angle between teta-rays direction and hyperfine field vector of iron, (), a monochromatic circularly polarized Mössbauer source (MCPMS) was used. The analysis of the MCPMS results show that the shapes of the measured spectra can be explained by single values of .

Hyperfine interactions in (Cr0.9957Fe0.01)3 + xSi1 - x

86%

Satuła D. , Szymański K. , Olszewski W. , Kalska-Szostko B. , Waliszewski J. , Rećko K.

2013

tom Vol. 58, No. 1

73-76

X-ray diffraction measurements and Mossbauer spectroscopy with external magnetic field were carried out on (Cr0.99 57Fe0.01)3+xSi-x alloys. The Mossbauer spectra for A15 type of structure can be described by superposition of single line S(1) and two doublets D(1) and D(2). The relative ratio of the S(1) and D(2) strongly depends on x. The nearest neighbours of these components have been identified. It was shown that 57Fe atoms preferentially locate in Cr positions for x less-than or equal to 0.0, while for x greater 0.0 iron atoms are distributed both in Cr and Si positions. It was shown that, in A15 structure, one Cr atom located in the 57Fe nearest neighbours (n.n.) decreases isomer shift by (0.022 plus or minus 0.002) mm/s, while one Si in n.n. increases isomer shift by (0.09 plus or minus 0.01) mm/s. The measured Mossbauer spectra of bcc Cr-Si indicate that atoms are randomly distributed and can be well described as superposition of single lines, related to various local environments of 57Fe atoms.