Abstract
Two-phase composites La0.7Sr0.3MnO3/Ta2O5 are synthesized and their magnetization and low-field magnetoresistance (LFMR) characteristics are investigated. It is found that a small amount of Ta ions enter into LSMO grains near the grain surface region, resulting in the reduction of the cell volume, and consequently, an extra reduction of the saturate magnetization. The paramagnetism-to-ferromagnetism transition temperature, TC, does not show significant change. The LFMR enhancement is observed over a wide range of temperature from 50 to 350K when the second phase material (Ta2O5) is introduced.
The magnetic disorder caused by the secondary phase at grain boundaries and the Ta doping effect on the surface of LSMO grains are believed to contribute to the enhanced MR.