aSchool of Chemistry and Environmental Science, Hebei University, Baoding 071002, PR China
Available online 16 October 2007.
Abstract
The structural, electrical transport and magnetic properties have been studied for compounds: La1−xSrxFe1−xMnxO3 (0.3 ≤ x ≤ 0.7). The lattice parameter, a, first decreases with x, and followed by an increase when Sr2+ and Mn4+ was continuously doped. The cell parameters, b and c, slightly decrease with coupled substitution of Sr2+ for La3+ and Mn4+ for Fe3+. In the paramagnetic temperature range, formation of magnetic clusters is suggested; the sizes of clusters decrease with x up to 0.5, following that they increase sharply with continuing doping. The electrical behaviors of all specimens demonstrate insulators and the electrical resistivity increases with content of Mn4+ and Sr2+ ions doped. A variable range hopping model is suitable to describe electrical transport process for the compounds at low temperature. At high temperature the electrical transport process can be described by bipolaron model for all compounds.
Keywords: Oxide materials; Magnetic measurements; Electrical transport; Solid-state reaction
Fig. 1. X-ray diffraction patterns for compounds La1−xSrxFe1−xMnxO3.
Fig. 2. Lattice parameters a, b, and c, as a function of x for compounds La1−xSrxFe1−xMnxO3.
Fig. 3. Temperature dependence of magnetization (M) measured under H = 0.5 T for compounds La1−xSrxFe1−xMnxO3.
Fig. 4. The reciprocal of magnetization (1/M) for samples La1−xSrxFe1−xMnxO3, the solid lines result from fits of the Curie–Weiss law to the experimental data.
Fig. 5. Curie–Weiss temperature dependence of the spontaneous orthorhombic strain for compounds La1−xSrxFe1−xMnxO3.
Fig. 6. Temperature dependence of the electrical resistivity for samples of the solid solution of La1−xSrxFe1−x MnxO3 (0.3 ≤ x ≤ 0.7).
Fig. 7. Plots of log R vs. T−1/4; inset: plots of log(R/T1/2) vs. 1/T for x from 0.3 to 0.7.
Table 1.
Values of spontaneous orthorhombic strain, and cell distortion factor and relations among cell parameters a, b and c
Table 2.
Values of parameters Cobs. and θ obtained from fittings of the reciprocal susceptibility data by Curie–Weiss law, and ideal Ccal. and Cobs./Ccal. for the samples La1−x SrxFe1−x MnxO3
