Magnetotransport and magnetic properties of La0.7MnO3-delta and Pr0.65Ba0.05Ca0.3MnO3-delta superlattices

Superlattice structures consisting of La0.7MnO3-delta (LMO) and Pr0.65Ba0.0 5Ca0.3MnO3-delta (PBCMO) systems, in which the thickness of La0.7MnO3-delta is fixed and that of Pr0.65Ba0.05Ca0.3MnO3-delta varied from 1 to 8 unit c ells, have been grown in situ on (100) LaAlO3 substrates using a pulsed-las er deposition technique. Microstructural characterization carried out on th ese films shows the presence of characteristic intense satellite peaks, ind icating the chemical modulation of the superlattice structure. The insulato r-to-metal transition and the magnetoresistance (MR) ratio are found to var y with the number of unit cells. The samples with 1, 2, 5, and 8 unit cells of Pr0.65Ba0.05Ca0.3MnO3-delta show transition temperatures of 240, 230, 1 50, and 160 K and MR ratios of 540%, 592%, 3150%, and 2875%, respectively. We have observed an enhancement of magnetoresistance ratios in the case of superlattices with a thickness of PBCMO greater than 5 unit cells, which ma y be attributed to a ferromagnetic biasing provided by the LMO layers actin g as a ferromagnetic film below its transition temperature. (C) 2001 Americ an Institute of Physics.