Structural, magnetic and magnetoresistive properties of La0.7Sr0.3-xNaxMnO3 manganites

We present the monovalent alkali metal substitution effects upon structural , magnetic and electrical properties in La0.7Sr0.3-xNaxMnO3 for 0 less than or equal to x less than or equal to 0.2. X-ray diffraction patterns show t hat our powder samples crystallize in a rhombohedral distorted perovskite s tructure with R (3) over barc space group. All the samples exhibit a ferrom agnetic-paramagnetic transition and metallic-semi-conductor one with increa sing temperature. The Curie temperature T-C decreases from 365 to 305 K; ho wever the resistivity transition temperature T-rho decreases from 340 to 27 0 K as Na content increases. A magnetoresistance ratio of about 46% at 300 K and in an applied field of 10 T has been observed in the bulk ceramic La0 .7Sr0.1Na0.2MnO3 sample.