Magnetotransport in Thin Films of Lan-nxCa1+nxMnnO3n+1 (n=2,3, and ∞)

With a use of the epitaxial a-axis thin films of perovskite series Lan-nxCa1+nxMnnO3n+1 (n=2,3, and ∞) with fixed carrier concentration (x=0.3), the transport properties of the series compounds have been examined to be associated with the difference in the number of the MnO2 layers. Results have indicated that a reduction in the number of layers results in systematic changes in the various features. These include an increase in resistivity, a decrease in resistivity peak temperature Tcρ corresponding to the metal-insulator transition, an enhancement of the maximum MR near Tcρ, and an increase in low temperature intrinsic MR. In order to explain the variation in these features with the number of MnO2 layers, it is necessary to take both anisotropie c-axis transfer interaction and two-dimensional spin fluctuation into account.