Evolution of thermoelectric properties in EuxYb1-xB6family

M A Anisimov; N A Samarin; V S Zhurkin; A V Bogach; S V Demishev; V V Voronov; N Yu Shitsevalova; A V Levchenko; V B Filipov; V V Glushkov

doi:10.1088/1361-648X/aba864

Evolution of thermoelectric properties in Eu_xYb_1-xB₆family

J Phys Condens Matter. 2020 Aug 20;32(46). doi: 10.1088/1361-648X/aba864.

Authors

M A Anisimov¹, N A Samarin¹, V S Zhurkin², A V Bogach^{1

3}, S V Demishev^{1

2}, V V Voronov¹, N Yu Shitsevalova⁴, A V Levchenko⁴, V B Filipov⁴, V V Glushkov¹

Affiliations

¹ Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 119991, Russia.
² Moscow Institute of Physics and Technology, Dolgoprudny 141700, Russia.
³ National University of Science and Technology "MISIS", Moscow 119049, Russia.
⁴ Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, Kiev 03680, Ukraine.

PMID: 32698166
DOI: 10.1088/1361-648X/aba864

Abstract

Seebeck effect in the crystalline samples of Eu_xYb_1-xB₆(x= 0, 0.082, 0.127, 0.9, 1) was investigated at temperatures 2-300 K. For all the compounds thermopower is shown to be well described by the sum of diffusion (S_d=AT) and phonon drag components. The latter contribution is induced by quasilocal (Einstein) modes of ytterbium and europium ions with characteristic temperatures Θ_E(YbB₆) ≈ 91 K and Θ_E(EuB₆) ≈ 122 K. The estimation of effective massm^*of the charge carriers proves that increasing of Eu content induces crossover from 'heavy' holes withm_h^*(x⩽ 0.127) ≈ 0.3-0.36m₀to 'light' electrons withm_e^*(x⩾ 0.9) ≈ 0.12-0.13m₀(m₀-free electron mass). For the Eu-rich compounds we propose the existence of additional point on the phase diagram, which corresponds to short-range magnetic order with enhanced spin fluctuations preceding the stabilization of magnetic polarons.

Keywords: EuB6; Seebeck effect; YbB6; diffusion thermopower; hexaborides; phonon drag; polarons.