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High-purity rare-earth metals for studying the magnetocaloric effect in a wide range of magnetic fields

N.B. Kolchugina1, Yu.S. Koshkid’ko2, J. Cwik 2, C. Salazar Mejia 3, V.I. Zverev4, N.A. Dormidontov1, P.A. Prokofev1, A.A. Bakulina 1, R.R. Gimaev 4, A.A. Nikitin 5

1 Baikov Institute of Metallurgy and Materials Sciences, Russian Academy of Sciences, Leninskii pr. 49, Moscow, 119334 Russia
2 Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wrocław, 50-950 Poland
3 Hochfeld-Magnetlabor Dresden (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany
4 Moscow State University, Faculty of Physics, Leninskie Gory 1, Moscow, Russia
5 National Research Center Kurchatov Institute, pl. Akademika Kurchatova 1, Moscow, 123182 Russia

Dr. Sci. Natalia B. Kolchugina

Head of Laboratory, Baikov Institute of Metallurgy and Materials Science of the Russian Academy of Sciences

Abstract. High-purity Dy and Tb are prepared by vacuum sublimation and distillation. The impurity compositions of the metals for the first time are estimated by atomic probe tomography. X-ray textural analysis, atomic-force microscopy, scanning electron microscopy also are used to determine the texture of the purified material and its grain structure. The metals are characterized by fine grained structure of crystallites and the dominant texture-less component. It was demonstrated the presence of nano-sized inclusion and clusters of gas-forming impurities. The magnetocaloric effect of sublimed Dy is studied by indirect (calculation of the isothermal magnetic entropy change in using magnetization data) method and direct measurements of the adiabatic temperature change ∆Tad in high steady (to 14 T) and ultrahigh pulsed (to 50 T) magnetic fields. For the first time, significant values of ∆Tadof Dy were observed experimentally by the direct measurements. The measurements in the high steady magnetic fields were performed in a temperature range of 4.2-350 K using an original installation. The maximum value of the ∆Tadof Dy is observed in the vicinity of the Néel temperature (179 K) and is 22 K in a steady field of 14 T and 51 K in a pulsed magnetic field of 50 K. Despite the absence of single-crystal structure and existence of misorientation of individual Dy crystallites, the values of the adiabatic temperature change ΔTad measured in pulsed fields are comparable with those observed for Dy single crystals along the a axis. The experimental data also confirm the theoretically predicted comparability of the values of ∆Tad of Dy and Gd, which are reached in ultrahigh pulsed field (50 T).

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