Laiho R, Lisunov K G, Lähderanta E, Stamov V S, Zakhvalinskii V S, Colomban Ph, Petrenko P A, Stepanov Yu P
Wihuri Physical Laboratory, University of Turku, FIN-20014 Turku, Finland.
J Phys Condens Matter. 2005 Jan 12;17(1):105-18. doi: 10.1088/0953-8984/17/1/011. Epub 2004 Dec 10.
Structural and transport properties of ceramic LaMnO(3+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 ([Formula: see text]) 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, T(C). In the field of 8 T the relative magnetoresistance, Δρ(B)/ρ(0), reaches at δ = 0.154 the values of -88% near T(C) and -98% at [Formula: see text] K. The resistivity of the PM phase of LaMnO(3+δ) with δ = 0.100-0.154 satisfies the Shklovskii-Efros-like variable-range hopping (VRH) conductivity law between [Formula: see text] K and the VRH onset temperature [Formula: see text] 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 [Formula: see text] eV and a rigid gap [Formula: see text] eV, the latter being connected to formation of small polarons.
研究了δ = 0 - 0.154时陶瓷LaMnO(3 + δ)的结构和输运性质。根据室温下的x射线衍射测量，该化合物的晶体结构从δ = 0时的正交晶系（Pbnm）变化到δ = 0.065 - 0.112时的菱形畸变立方晶系（Pm3m），再到δ = 0.125 - 0.154时的菱面体（[化学式：见原文]）晶体对称性。这些结构变化通过拉曼显微光谱测量得到证实。在δ = 0 - 0.154范围内，电阻率在顺磁（PM）到铁磁转变温度T(C)之上和之下均表现出激活行为。在8 T的磁场中，δ = 0.154时，相对磁电阻Δρ(B)/ρ(0)在T(C)附近达到 - 88%的值，在[化学式：见原文] K时达到 - 98%。δ = 0.100 - 0.154的LaMnO(3 + δ)的PM相电阻率在[化学式：见原文] K和VRH起始温度[化学式：见原文] K之间满足类Shklovskii - Efros变程跳跃（VRH）电导率定律。电阻率由费米能级附近局域态密度的复杂能量依赖性决定，包括一个软库仑能隙[化学式：见原文] eV和一个刚性能隙[化学式：见原文] eV，后者与小极化子的形成有关。
