A1 Journal article (refereed), original research

Lattice distortions, magnetoresistance and hopping conductivity in LaMnO3+δ


Publication Details

Authors: Laiho R, Lisunov K G, Lähderanta Erkki, Stamov VS, Zakhvalinskii V S, Ph Colomban PH, Petrenko PA, Stepanov Yu P

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: 1

Start page: 105

End page: 118

Number of pages: 14

ISSN: 0953-8984

eISSN: 1361-648X

JUFO level of this publication: 0

Digital Object Identifier (DOI): http://dx.doi.org/10.1088/0953-8984/17/1/011

Open Access: Not an Open Access publication


Abstract

Structural and transport properties of ceramic LaMnO3+δ are
investigated for δ = 0–0.154. According to x-ray diffraction
measurements at room temperature the crystal structure of this compound
varies from orthorhombic (Pbnm) for δ = 0 to rhombohedrally distorted cubic (Pm3m) for δ = 0.065–0.112 and to rhombohedral (Rar {3}c )
crystal symmetry for δ = 0.125–0.154. These structural modifications
are confirmed by the Raman micro-spectroscopy measurements. The
resistivity displays in the range δ = 0–0.154 an activated behaviour
both above and below the paramagnetic (PM) to ferromagnetic transition
temperature, TC. In the field of 8 T the relative magnetoresistance, Δρ(B)/ρ(0), reaches at δ = 0.154 the values of −88% near TC and −98% at Tapprox 20 K. The resistivity of the PM phase of LaMnO3+δ with δ = 0.100–0.154 satisfies the Shklovskii–Efros-like variable-range hopping (VRH) conductivity law between T_{mathrm {C}} sim 130mbox {--}160 K and the VRH onset temperature T_{mathrm {v}}sim 250mbox {--}270 K.
The resistivity is governed by a complex energy dependence of the
density of the localized states near the Fermi level, comprising a soft
Coulomb gap Delta approx 0.43mbox {--}0.48 eV and a rigid gap gamma approx 0.14mbox {--} 0.17 eV, the latter being connected to formation of small polarons.


Last updated on 2019-09-10 at 14:46