Tunneling magnetoresistance in nanogranular La1-xSrxMnO3 (x∼0.5)

Electric transport and magnetic studies were performed on the La1-xSrxMnO3 (x=0.45-0.55) perovskite manganites. The main focus was given to the nanogranular ceramics of average x=0.47 composition, compacted by spark plasma sintering of molten salt synthesized nanoparticles. This sample can be viewed as a two-phase composite where FM manganite granules are embedded in AFM manganite matrix. The magnetoconductance data observed on this sample reveal a coexistence of distinct low- and high-field contributions, related to the field-induced alignment of ferromagnetic (FM) granules and the spin canting in antiferromagnetic (AFM) matrix, respectively. Their analysis confirms the theoretically predicted scaling of the low-field effect with squared reduced magnetization and provides also a quantitative comparison between the linear coefficient of high-field magnetoconductance and paraprocess seen in the magnetization measurement.