Evolution of thermoelectric properties in Eu x Yb 1-x B 6 family

• Published in: Journal of physics. Condensed matter Vol. 32; no. 46; p. 465601
• Main Authors: Anisimov, M A, Samarin, N A, Zhurkin, V S, Bogach, A V, Demishev, S V, Voronov, V V, Shitsevalova, N Yu, Levchenko, A V, Filipov, V B, Glushkov, V V
• Format: Journal Article
• Language: English
• Published: England 04.11.2020
• Subjects: phonon drag; YbB6; diffusion thermopower; hexaborides; EuB6; polarons; Seebeck effect
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/1361-648X/aba864

Seebeck effect in the crystalline samples of Eu Yb B ( = 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 ( = ) and phonon drag components. The latter contribution is induced by quasilocal (Einstein) modes of ytterbium and europium ions with characteristic temperatures Θ (YbB ) ≈ 91 K and Θ (EuB ) ≈ 122 K. The estimation of effective mass of the charge carriers proves that increasing of Eu content induces crossover from 'heavy' holes with ( ⩽ 0.127) ≈ 0.3-0.36 to 'light' electrons with ( ⩾ 0.9) ≈ 0.12-0.13 ( -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.