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 ≤ x ≤ 0.2. X-ray diffraction patterns show that our powder samples crystallize in a rhombohedral distorted perovskite structure with R3̄c space group. All the samples exhibit a ferromagnetic-paramagnetic transition and metallic-semi-conductor one with increasing temperature. The Curie temperature TC decreases from 365 to 305 K; however the resistivity transition temperature Tρ decreases from 340 to 270 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.