Complex oxide-based magnetic tunnel junctions with nonmagnetic insulating barrier layers

Magnetic tunnel junctions composed of the colossal magnetoresistance material La0.7Sr0.3MnO3 (LSMO) and magnetite (Fe3O4) have been fabricated and characterized. The films were grown on (110) SrTiO3 substrates using pulsed laser deposition, with the nonmagnetic spinel Mg2TiO4 (MTO) chosen as the barrier layer in order to provide a well lattice-matched isostructural interface with the Fe3O4 electrode. Junction magnetoresistance (JMR) values of up to -26% were observed for junctions with 50-angstrom-thick MTO barriers at 70 K. Measurements were performed on junctions with barrier thicknesses ranging from 50-120 angstrom. The resistance jumps in JMR correspond well to the switching fields of the LSMO and Fe3O4 magnetic electrodes. The magnitude of the JMR peaks and then begins to decline with decreasing temperature, indicating that prior observations of such temperature-dependent JMR behavior in CoCr2O4 barrier junctions were due to the electrode at low temperatures rather than to magnetic moments in the CoCr2O4. (C) 2006 American Institute of Physics.