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Specific features of thermal and magnetic properties of YbB50 at low temperatures

TitleSpecific features of thermal and magnetic properties of YbB50 at low temperatures
Publication TypeJournal Article
Year of Publication2018
AuthorsNovikov, VV, Zhemoedov, NA, Matovnikov, AV, Mitroshenkov, NV, Popova, EA, Tolstosheev, AK, Malkin, BZ, Bud'ko, SL
JournalPhysical Review Materials
Date Published05
Type of ArticleArticle
ISBN Number2475-9953
Accession NumberWOS:000432994800001
Keywordsanomalies, boride, boron-rich phases, crystal-electric-field, expansion, growth, heat-capacity, lattice, Materials Science, semiconductors, transition

Heat capacity, thermal expansion, and magnetization of ytterbium boride YbB50 were studied at temperatures 0.6-300 K, 5-300 K, and 2-300 K, respectively. We revealed two smooth peaks at about 4.0 and 60 K in the temperature dependence of the heat capacity. A comparison with the heat capacity of the diamagnetic isostructural boride LuB50 shows that these anomalies can be attributed to excitations in the ytterbium sublattice (Schottky anomalies). A scheme for splitting of the ground F-2(7/2) multiplet of Yb3+ ions in the crystal field is proposed. Reliability of the proposed crystal-field energies of the Yb3+ ions is confirmed by the analysis of temperature dependencies of magnetic susceptibility and magnetization in applied magnetic fields up to 55 kOe. A clear anisotropy of the thermal expansion and a negative expansion within a wide temperature range (40-185 K) were observed. Assuming that this anomaly of the thermal expansion in higher borides is caused by the specific thermal evolution of a crystal lattice observed earlier, in particular, in LuB50, and the interaction of rare-earth ions with lattice strains, we have determined phenomenological Gruneisen parameters which characterize effects due to thermal transitions of Yb3+ ions between the ground and excited states. A phase transition of YbB50 to any magnetically ordered state was not observed down to the lowest temperatures of experiments.

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