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1
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Inelastic Neutron Scattering Investigation of Magnetic Excitations in the Quenched and Decomposed Samples of the Mn_{0.75}Cu_{0.25} Alloy

100%
Jankowska-Kisielińska J., Świderska K.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
990-993
EN
The influence of spinodal decomposition on the spin wave characteristics in the Mn_{0.75}Cu_{0.25} alloy was studied with inelastic neutron scattering. The measurements were performed on the quenched and annealed samples at a few temperatures. Parameters of spin-wave dispersion-relation for small wave-vector were derived. The values of spin wave velocity and energy gap obtained at reduced temperature T/T_{N} ≈ 0.65 are after decomposition twice higher than for the quenched sample. For the decomposed sample the values of both parameters are close to the results published for the Mn_{0.9}Cu_{0.1} alloy. This fact confirms that after decomposition spin waves are present in the sample regions of Cu concentration close to 0.1 and that the neighborhood of regions with high Cu content seems not to influence them. The spin wave velocity for the quenched sample is lower than observed in any other manganese alloy.
2
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The Effect of Phase Decomposition on Magnetic Structure of Cu_{0.4}Mn_{0.3}Ni_{0.3} Alloy

100%
Świderska K., Jankowska-Kisielińska J.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
394-396
EN
The purpose of present investigation was to study the effects of phase decomposition of the Cu_{0.4}Mn_{0.3}Ni_{0.3} alloy on its magnetic ordering. The single-crystal sample was examined by elastic neutron scattering before and after five subsequent annealing runs. The results indicate that in small fraction of the quenched sample volume there are two types of antiferromagnetic order: one of them AF1 of the long range, the other one of the short range. Ageing induces phase decomposition which yields disappearance of AF1 long range order and increase of the volume of new ordered phase. The results of the investigations of the aged sample indicate that regions of new tetragonal phase exhibit antiferromagnetic ordering with magnetic moments of Mn atoms arranged as in the pure compound MnNi but with unequal domain distribution. The intensity of magnetic component of super-structure reflections increases with the duration of ageing at lower rate than component due to atomic order.
3
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Diffuse Neutron Scattering in the Mn_{0.4}Cu_{0.6} Alloy

81%
Jankowska-Kisielińska J., Mikke K., Fijał-Kirejczyk I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 4
1171-1178
EN
The diffuse neutron scattering in the Mn_{0.4}Cu_{0.6} alloy was measured in the temperature range 15-390K at the 3-axis neutron spectrometer at MARIA reactor in Świerk. The broad maxima of the neutron intensity were observed in the surrounding of the (0.5, 1, 0) reciprocal lattice point and other symmetry related points. The effect is similar to that observed in Mn-Cu alloys with lower Mn content at room temperature. Our results are in agreement with the earlier finding that the maxima of the short-range order incommensurate spin density wave scattering are placed at the (0.5±δ, 1, 0) reciprocal lattice point with a linear dependence of δ on the Mn concentration. In addition, some commensurate antiferromagnetic short-range order was found.
4
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Inelastic Neutron Scattering in Sendust Alloy in 8-295 K Temperature Range

81%
Świderska K., Jankowska-Kisielińska J., Dobrzyński L.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
400-404
EN
The effects concerning magnetic and nuclear excitations in a single crystal of Sendust alloy (73.5 at.% Fe, 9.5 at.% Al, 17 at.% Si) are discussed. The excitations have been investigated by means of elastic and inelastic neutron scattering with the use of triple axis and small angle spectrometer. A few potential causes of spin wave damping in Sendust, like interactions of excitations or small-size precipitations of different compositions or directions of magnetization were disproved. It is suggested that one- and two-phonon scattering can explain observed strong increase of incoherent inelastic scattering with temperature.
5
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Anisotropy of the Neutron Scattering in the Paramagnetic Phase and on the Spin Waves in the Mn_{0.71}Ni_{0.29} Alloy

81%
Jankowska-Kisielińska J., Fijał-Kirejczyk I., Mikke K.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
203-205
EN
We have confirmed the significant anisotropy of the generalised magnetic susceptibility in the paramagnetic and antiferromagnetic phase of the fcc Mn-Ni alloys. In this paper the detailed account of the experiments performed on the Mn_{0.71}Ni_{0.29} alloy is given. Our main result for the paramagnetic phase is that the correlation length is larger for the direction parallel to the anisotropy axis than for the perpendicular one by a factor of 1.6. The spin-wave velocity observed at 15 K is higher for the direction parallel to the anisotropy axis than that for the perpendicular direction by a factor of 1.2. These results are similar to that for the Mn_{0.62}Ni_{0.38} alloy. Our results indicate that the magnetic carriers are more localized and the magnetic interactions are less extended in alloys with higher Ni concentration.
6
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Structure and Short Range Order of Two Phases in the Single Domain Mn_{0.75}Cu_{0.25} Alloy after Spinodal Decomposition

81%
Jankowska-Kisielińska J., Świderska K., Mikke K.
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issue 4
582-585
EN
The aim of the present paper was to identify the atomic and magnetic structure and short-range order of the two phases present in the Mn_{0.75}Cu_{0.25} alloy after decomposition and plastic deformation. The sample was investigated by elastic neutron scattering at small-angle and 3-axes spectrometers. We have confirmed the decomposition of the alloy into two types of regions with manganese concentration increased and decreased as compared with the mean value. The crystal lattice in regions of both types is tetragonal (pseudo FCT) below T_{N} but degree of tetragonal distortion is different. The long range antiferromagnetic order is present only in the regions of bigger distortion and higher Mn concentration. In the regions of lower Mn content and smaller distortion there is a short range ordering of complex magnetic and atomic character.
7
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Inelastic Neutron Scattering in γ-Mn(12%Ge) Alloy Above and Below the Néel Temperature

81%
Jankowska-Kisielińska J., Mikke K., Hennion B.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
559-562
EN
The magnetic excitations different from spin waves in the γ-Mn(12%Ge) antiferromagnet are the subject of the present investigation. The inelastic neutron scattering was measured at 4 temperatures above T_{N}. The Lorentzian-type formula for the inelastic neutron scattering cross-section with the spectral width for a hydrodynamic region was used for data analysis. The obtained values of the "stiffness constants" are of the order of 200 meV Å and they depend weakly on temperature in the range of 1.04-1.25T_{N}. The inelastic neutron scattering for energy transfers below and close to the value of the gap energy of the spin wave spectrum was measured at room temperature. The observed intensities can be treated as a sum of intensities of neutrons scattered on spin waves around the magnetic Brillouin zone centre and = those scattered on fluctuations at the zone boundary.
8
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Temperature Dependence of Magnetic Inelastic Neutron Scattering in Mn(12%Ge) Alloy

71%
Jankowska-Kisielińska J., Mikke K., Milczarek J. J., Hennion B., Udovenko V. A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
483-486
EN
A systematic study of temperature dependence of magnetic inelastic neutron scattering for itinerant antiferromagnet Mn(12%Ge) is presented. At low temperatures the experimental data are well described in terms of damped spin waves. This description becomes insufficient at least 150 K below T_{N}. In the temperature range 200-400 K the integrated intensity of distribution for energy transfer 13 THz increases by one third and the shape of the deconvoluted neutron scattering cross-section changes. These changes suggest that ca. 200 K below T_{N} an additional contribution to the inelastic neutron scattering starts to appear and that its origin is different from spin waves.
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