Enhanced electro-magnetic properties in La_0.7Sr_0.3MnO₃/ZrO₂ composites

(La_0.7Sr_0.3MnO₃)_1−x /(ZrO₂)_x (x = 0.0–0.150, step 0.025) composites have been prepared via solid state reaction process. The X-ray diffraction and scanning electron microscopic observations indicate that there are ZrO₂ grains separated from La_0.7Sr_0.3MnO₃ matrix. It has been found that the inclusion of ZrO₂ content decreases the conductivity, magnetization and metal–semiconductor transition, whereas it increases the low field magnetoresistance. Possible effects of grain boundaries on the low field magnetoresistance have been discussed. The small ZrO₂ grains are trapped between La_0.7Sr_0.3MnO₃ grains may be acting as a barrier for spin-polarized tunneling and enhance the low-field magnetoresistance. (author)