A1 Journal article (refereed), original research

Mechanism of hopping conductivity in weakly doped La1-xBaxMnO3


Publication Details

Authors: Laiho R, Lisunov K G, Lähderanta Erkki, Shakhov M A, Stamov V N, Zakhvalinskii V S, Kozhevnikov VL, Leonidov I A, Mitberg E B, Patrakeev M V

Publisher: IOP Publishing: Hybrid Open Access

Publication year: 2005

Language: English

Related journal or series: Journal of Physics: Condensed Matter

Volume number: 17

Issue number: 21

Start page: 3429

End page: 3444

Number of pages: 16

ISSN: 0953-8984

eISSN: 1361-648X

JUFO level of this publication: 0

Digital Object Identifier (DOI): http://dx.doi.org/10.1088/0953-8984/17/21/033

Open Access: Not an Open Access publication


Abstract

The resistivity, ρ, of ceramic La1−xBaxMnO3 with x = 0.02–0.10 corresponding to the concentrations of holes c≈0.15–0.17 displays an activated behaviour both above and below the paramagnetic to ferromagnetic transition temperature TC = 175–209 K, obtained from measurements of the magnetization. Above T~310–390 K ρ(T,x) is determined by nearest-neighbour hopping of small polarons with activation energy Ea = 0.20–0.22 eV. Below the onset temperature Tv = 250–280 K, depending on x,
a Shklovskii–Efros-like variable-range hopping conductivity mechanism,
governed by a soft temperature independent Coulomb gap, Δ≈0.44–0.46 eV,
and a rigid gap, δ(T), is found. For the range T~50–120 K, δ(T)
is connected to the formation of small lattice polarons in conditions
of strong electron–phonon interaction and lattice disorder. The rigid
gap obeys a law δ(T)~T1/2 within two temperature intervals above and below TC, exhibits an inflection at TC and reaches at Tv a value of δv≈0.14–0.18 eV. Such behaviour suggests a spin dependent contribution to δ(T). The localization radius of the charge carriers, a, has different constant values within the temperature intervals where δ(T)~T1/2. With further decrease of T, a increases according to the law expected for small lattice polarons.


Last updated on 2019-10-10 at 14:20