Temperature Stability of Magnetoresistance around Room Temperature in Perovskite Materials La0.60Sr0.40-xNaxMnO3
Perovskite rare-earth manganites polycrystalline samples formulated as La0.60Sr0.40-xNaxMnO3 (x = 0. 00, 0. 10, 0. 15, 0. 20, 0. 30, 0. 33, 0. 35) were synthesized by sol-gel method. It is found that when Sr+2 ions were partly substituted by Na+1 ions, the Curie temperature of the substituted samples decreased to room temperature and the room temperature magnetoresistance (MR) increased obviously than un-substituted La0.60Sr0.40MnO3. Under an applied filed of 1. 8T, the maximum MR for the sample La0.60Sr0.07 Na0.33 MnO3 at 292 K was 24. 4% , 2. 8 times more than La0.60Sr0.40MnO3; and there was a stable MR of 3. 9%(±0. 2%) in the temperature range of 285K to 345K for the sample La0.60Sr0.25 Na0.15MnO3. Therefore, the room temperature magnetoresistance and the temperature stability of MR were obviously improved. Up to now, no similar reports have been found concerning so good temperature stability of MR in so wide temperature range around room temperature. These are prpbably significant to magnetoresistance materials application.
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