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

We report the transport and magnetoresistance (MR) measurements in a ferrom agnet-insulator-ferromagnet trilayer junction grown by pulsed laser deposit ion. The colossal magnetoresistive (CMR) manganite La0.55Ho0.15Sr0.3MnO3 is used as the ferromagnet layer and the compound La2BaNbO6 is used as the in sulating spacer, We observe that the transport properties across the juncti on 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 trans port properties of CMR-insulator-CMR trilayer junctions. The MR of the devi ce shows a significant enhancement at low field at temperatures below 100 K compared to the polycrystalline film of the same material grown on polycry stalline yttria-stabilised zirconia substrate. (C) 2001 Published by Elsevi er Science Ltd.