Phonon Drag and Magnetic Anomalies of Thermopower in RB12 (R = Ho, Er, Tm, Lu)

V. Glushkov a, S. Demishev a, M. Ignatov a, E. Khayrullin a, N. Sluchanko a, N. Shitsevalov ag b, A. Levchenko b, V. Filipov b, K. Flachbart c and K. Siemensmeyer d a A.M. Prokhorov General Physics Institute of RAS, 38, Vavilov str., Moscow, 119991, Russia b Institute for Problems of Materials Science of UAS, 3, Krzhyzhanovsky str., 03680 Kiev, Ukraine c Center of Low Temperature Physics, IEP SAS, 04001 Košice, Slovakia d Hahn-Meitner Institute, 100, Glienicker Str., 14109 Berlin, Germany

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Received: 9 07 2007;

High precision measurements of the Seebeck coefficient S(T) were carried out on the single crystals of RB12 (R = Ho, Er, Tm, Lu) at temperatures 2-300 K. It was shown that the effects of phonon drag result from vibrations of rare earth ions (ℏ ωE≈10-33 meV) in the rigid framework structure of the B12 clusters and determine the main contribution to thermopower at intermediate temperatures (30-300 K). The correlated behavior of transport parameters favors the appreciable enhancement of spin fluctuations in the sequence of magnetic compounds (HoB12-TmB12) when approaching to the valence instability state in YbB12. The giant increase in S(T) detected in the vicinity of the Néel temperature TN for HoB12, ErB12, and TmB12 seems to result from the density of states renormalization caused by antiferromagnetic ordering.

DOI: 10.12693/APhysPolA.113.275 PACS numbers: 72.15.Jf, 75.50.Ee