Electrical transport and magnetic properties of La_0.67Ca_0.33Mn_1−xCr _xO₃ and La0_.67+xCa_0.33−x Mn_1−xCr _xO₃(0.04≤x≤0.08)

Abstract

A comparative study for two different series, La_0.67Ca_0.33Mn_1−xCr _xO₃ and La_0.67+xCa_0.33−xMn_1−xCr _xO₃, is performed with χ changing from 0.04 to 0.08 through measurements of zero-field resistivity (π), magnetoresistance (MR) and ac susceptibility (χ) as functions of temperature (T). For the second group, a single insulator-metal transition was characterized by the resistivity maximum appears in π vs. T curve. For the first group, besides the resistivity peak appearing at higher temperatures, the sample shows evidence for the existence of another peak appearing at lower temperatures. Compared to the first group, the second group shows a significant enhancement in MR effect, while the measurement of χ-T dependence does not display obvious differences for the two series. Different behaviors observed in the two series are discussed by considering possible exchange interaction between Mn³⁺ ion and Cr³⁺ ion.

Keywords

perovskite manganites / double exchange / metal-insulator transition / colossal magnetoresistance

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