Transport and magnetoresistive properties of an imperfect ferromagnet–insulator–ferromagnet trilayer junction

We report the transport and magnetoresistance (MR) measurements in a ferromagnet–insulator–ferromagnet trilayer junction grown by pulsed laser deposition. The colossal magnetoresistive (CMR) manganite La0.55Ho0.15Sr0.3MnO3 is used as the ferromagnet layer and the compound La2BaNbO6 is used as the insulating spacer. We observe that the transport properties across the junction are well described by considering a network of parallel paths involving an insulating and a metallic channel. These results demonstrate the role of imperfections in the form of pinholes in the insulating layer on the transport properties of CMR–insulator–CMR trilayer junctions. The MR of the device shows a significant enhancement at low field at temperatures below 100 K compared to the polycrystalline film of the same material grown on polycrystalline yttria-stabilised zirconia substrate.