High-resolution neutron Fourier diffractometer with wide-aperture detector Sergey V. Sumnikov, Bekarys Yerzhanov, Roman N. Vasin, Dmitry A. Balagurov, Vasil M. Milkov, Maxim M. Podlesnyy, Andrey A. Bogdzel, Valery V. Zhuravlev, Nikolay D. Zernin, Sergey A. Kulikov, Viktor I. Bodnarchuk, Anatoly M. Balagurov Journal of Applied Crystallography, 2026 The high-resolution neutron Fourier diffractometer (HRFD), implementing the correlation method of diffraction data acquisition, has been successfully operated at the IBR-2 pulsed reactor in the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research for more than 30 years. This paper summarizes the results of upgrading the main units of the HRFD (the Fourier chopper, neutron guide and data acquisition electronics have been replaced with new, modern counterparts) and presents the first results of commissioning a new wide-aperture scintillation detector with a total sensitive-elements area of about 13 m 2 and a total solid angle of about 2.0 sr. The newly emerged opportunities for studying the atomic and magnetic structures of crystalline materials and their evolution in real time are discussed.
Estimation of the Coherently Scattering Domain Size in Alloys from Neutron Diffraction Data B. Yerzhanov, I. A. Bobrikov, A. M. Balagurov Journal of Surface Investigation, 2024 Abstract To determine the size distribution of structurally ordered clusters dispersed within a structurally disordered alloy matrix, we analyze the diffraction patterns of the Fe74Al26 alloy obtained using a high-resolution neutron diffractometer. This analysis employs the generalized Scherrer method, which involves analyzing diffraction-peak profiles, determining peak widths at heights of 1/5 and 4/5 of the maximum, and assuming a gamma distribution for cluster sizes (Pielaszek method). We compare the results obtained using the Scherrer, Williamson–Hall, and Pielaszek methods, finding them to agree. We propose an algorithm to calculate the log-normal distribution function of cluster/particle sizes. Experimental data are obtained using a time-of-flight neutron diffractometer. The analysis is conducted for two scanning variable options: in the crystallographic (direct) (d scale) and reciprocal (H scale) spaces, and possible systematic errors are evaluated. We conclude that the average sizes determined in this manner possess the necessary degree of stability, showing a weak dependence on the applied scanning variable and the total number of experimental points.
Tetragonal phases in Fe-Ga alloys: A quantitative study A. M. Balagurov, I. A. Bobrikov, D. Yu. Chernyshov, A. S. Sohatsky, S. V. Sumnikov, B. Yerzhanov, I. S. Golovin Physical Review Materials, 2024 Currently, the dominant model for the formation of enhanced magnetostriction of Fe-Ga alloys is based on the assumption of the presence of microscopic inclusions with a tetragonal $L{6}_{0}$ structure in the cubic matrix of the alloy. However, no evidence for the presence of this phase in the bulk of the alloys in amounts sufficient to have a noticeable effect on the magnitude of magnetostriction has been obtained so far. To test this hypothesis, a detailed scanning of the reciprocal space of $\mathrm{F}{\mathrm{e}}_{81}\mathrm{G}{\mathrm{a}}_{19}\mathrm{T}{\mathrm{b}}_{0.1}$ and ${\mathrm{Fe}}_{73}{\mathrm{Ga}}_{27}$ single crystals was carried out at ESRF at high photon flux stations. In particular, it was possible to reliably record superstructure diffraction peaks, the intensity of which was at a level of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ from the intensity of the fundamental peaks. Nevertheless, neither the presence of superstructure diffraction peaks obviously belonging to the $L{6}_{0}$ phase nor the tetragonal splitting of the fundamental diffraction peaks into components, which could indicate the presence of this phase in the samples, was detected. Similar results were obtained using complementary methods (electron and neutron diffraction). Based on the performed analysis of the background level in the places of the expected positions of superstructure peaks of the $L{6}_{0}$ phase, it was found that the volume fraction of this phase in the $\mathrm{F}{\mathrm{e}}_{81}\mathrm{G}{\mathrm{a}}_{19}\mathrm{T}{\mathrm{b}}_{0.1}$ alloy cannot exceed 0.2 %. The presence of a previously discovered $X$ phase with hexagonal or orthorhombic symmetry in a crystal with 27 at. % Ga was confirmed.
Phase States and Structural Phase Transitions in Fe73Ga27RE0.5 (RE = Dy, Er, Tb, Yb) Alloys: A Neutron Diffraction Study A. M. Balagurov, B. Yerzhanov, B. Mukhametuly, N. Yu. Samoylova, V. V. Palacheva, S. V. Sumnikov, I. S. Golovin Physics of Metals and Metallography, 2024 Abstract— New data on phase states and structural phase transitions in alloys Fe73Ga27 doped with Dy, Er, Tb, and Yb in an amount of about 0.5 at % are presented. Structural data were obtained in neutron diffraction experiments performed with high resolution and in continuous temperature scanning mode during heating to 850°C and subsequent cooling at a rate of ±2°C/min. It has been established that both the sequence of forming and disappearing structural phases and the final state of the alloy depend on the type of rare earth element. Phase transitions in the alloy with Dy are similar to those in the initial Fe73Ga27 alloy, excluding the final state. The procedure of doping with Er and Tb leads to the formation of disordered A1 and A3 phases instead of the L12 and D019 ordered close packed phases, respectively. In the case of doping with Yb, neither of the above phases is observed. The formation of the L60 (m-D03) and D022 tetragonal structural phases previously discovered in similar alloys by the electron diffraction method is not confirmed.
Order–Disorder Phase Transitions in Fe81Ga19–RE Alloys (RE = Dy, Er, Tb, Yb) According to Neutron Diffraction Data A. M. Balagurov, B. Yerzhanov, B. Mukhametuly, N. Yu. Samoylova, V. V. Palacheva, S. V. Sumnikov, I. S. Golovin Physics of Metals and Metallography, 2024 Abstract—New data on the phase compositions and structural transformations in a number of Fe81Ga19 alloys doped with trace amounts (≤0.2 at %) of rare earth elements are presented. The data were obtained in neutron diffraction experiments performed with high resolution and in a continuous temperature scanning mode under heating to 900°C and subsequent cooling. It has been established that structural rearrangements generally proceed in an identical manner both in the original Fe81Ga19 alloy and in its doped analogues. Slow heating and subsequent cooling of the alloys (at a rate of ±2°C/min) leads to the formation of clusters of the D03 phase with sizes in the range of 200–300 Å in the matrix of the disordered A2 phase. The sizes and volume fraction of clusters (~0.3 of the sample volume) weakly depend on a specific composition. The degree of ordering of the atomic structure of clusters changes with temperature according to a phase transition of the second kind and is close to unity at room temperature. The search for structural ordering corresponding to the modified D03 phase, which was discovered in a number of electron-diffraction studies, did not lead to a positive result.
