Enhanced room temperature magnetoresistance in maganites La 0.60Sr 0.25− yNa 0.15Δ y MnO 31

Abstract

Bulk polycrystalline samples of La 0.60Sr 0.4MnO 3 and La 0.60Sr 0.25− y Na 0.15Δ y MnO 3 with 0.00 ≤ y ≤ 0.15 (“Δ” representing cation vacancy) were successfully synthesized using the sol-gel method. The structural, magnetic, and electrical properties of the polycrystalline of the samples were investigated. The results of X-ray powder diffraction patterns show that these compounds crystallize in a distorted rhombohedral structure with the space group R ▪ C. The measurement shows that, with vacancy content y increasing, the unit cell volume V of samples increases, furthermore, the Curie temperature T c decreases. The temperature dependence of resistivity shows that all samples undergo a metal-semiconductor transition accompanying a ferromagnetic to paramagnetic transition with the increase of temperature. Under an applied filed of 1.8 T, a maximum room temperature magnetoresistance ( MR) of 20% is obtained at 293 K for the compound La 0.60Sr 0.1Na 0.15Δ 0.15MnO 3. The MR peak value of La 0.60Sr 0.1Na 0.15Δ 0.15MnO 3 increases 2 times more than that of La 0.60Sr 0.40MnO 3(MR p = 6.4%, T MR = 373 K), and the MR peak is shifted from 373 K to room temperature.