Magnetotransport in the La1.2(Sr, Ca)1.8Mn2O7 solid solution

High-quality single crystals of La1.2Sr1.8-y Cay Mn2O7 (0≤y≤0.2) were studied by means of electrical resistivity and magnetoresistance measurements. They exhibit a phase transition to a metallic ferromagnetic state at low temperature and strongly anisotropic electronic transport properties, which result from their lamellar structure. The temperature range of the resistivity measurements is extended up to about 1000 K, which allows us to discriminate between different theoretical models. In addition, an accurate comparison of parallel and perpendicular resistivity is carried out in order to reveal the effect of the two-dimensional magnetic correlations. The effect of disorder achieved by substitution of Ca2+, of smaller ionic radius, for Sr2+ is also investigated in detail. (author)