Metallic manganite oxides, La_(1-x)D_xMnO_3 (D chemical bounds Sr, Ca, etc.), display "colossal" magnetoresistance (CMR) near their magnetic phase transition temperatures (T_c) when subject to a Tesla-scale magnetic field. This phenomenal effect is the result of the strong interplay inherent in this class of materials among electronic structure, magnetic ordering, and lattice dynamics. Though fundamentally interesting, the CMR effect achiev ed only at large fields posses severe technological challenges to potential applications in magnetoelectronic devices, where low field sensitivity is crucial. Among the objectives of our research effort involvinb manganite materials is to reduce the field scale of MR by designing and fabricating tunnel junctions and other structures rich in magnetic domain walls. the junction electrodes were jmade of doped manganite epitaxial films, and the insulating barrier of SrTiO_3. The interfacial expitaxy has been imaged by using high-resolution transmission electron microscopy (TEM). We have used self-aligned lithographic process to pattern the junctions to micron scale in size. Large MR values close to 250
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