Observation of spin-dependent tunneling and large magnetoresistance in La{sub 0.7}Sr{sub 0.3}MnO{sub 3}/SrTiO{sub 3}/La{sub 0.7}Sr{sub 0.3}MnO{sub 3} ramp-edge junctions

Abstract

The authors have fabricated ferromagnet-insulator-ferromagnet tunneling junctions using a ramp-edge geometry based on (La{sub 0.7}Sr{sub 0.3})MnO{sub 3} ferromagnetic electrodes and a SrTiO{sub 3} insulator. Pulsed laser deposition was used to deposit the multilayer thin films and the devices were patterned using photolithography and ion milling. As expected from the spin-dependent tunneling, the junction magnetoresistance is dependent on the relative orientation of the magnetization in the electrodes. A junction magnetoresistance (JMR) as large as 30% is observed at low temperatures and low fields. In additino, they have found that JMR is reduced at high temperatures (T > 100 K) and decreases monotonically with increasing field at high fields (0.5 T < H < 1 T). Possible causes for these are also discussed