Enhanced room temperature magnetoresistance in La_0.7Ca_0.2Sr_0.1MnO₃/Ag composites

Abstract

The effect of added Ag on the electro-magnetic properties and enhanced room temperature magnetoresistance in (La0.7Ca0.2Sr0.1MnO3)1−x/Agx composites has been studied systematically. According to the results of x-ray diffraction, scanning electron microscopy and magnetic measurement, we can suggest that Ag segregates at the grain surface of La0.7Ca0.2Sr0.1MnO3. The results of electronic measurements show that the intrinsic insulator/metal transition temperature (TP) does not change, which is in accordance with the results for the Curie temperature (TC). It is very interesting to note that the magnetoresistance at room temperature is enhanced, which is encouraging for potential applications. These phenomena can be explained by considering that Ag, which segregated at the grain boundaries or surfaces, does not change the intrinsic structure of La0.7Ca0.2Sr0.1MnO3 and lead to a modification of grain boundaries.

Electrical properties and enhanced room temperature magnetoresistance in (La0.7Ca0.2Sr0.1MnO3)1−x/Pdx composites

“…From it, we can see that the of the samples reduce rapidly and their T p shift successively towards a higher temperature with the increase of Pd concentration until x = 0.25. This is in contrast to the composites La 0.7 Ca 0.2 Sr 0.1 MnO 3 -ZnO [7] and [18], but the same as La 0.67 (Ca 0.65 Ba 0.35 ) 0.33 MnO 3 -Pd [16,17] and La 0.7 Ca 0.2 Sr 0.1 MnO 3 /Ag [19]. However, when x > 0.25, the increases [16][17][18] and the T p falls.…”

“…Generally, metal Pd improves the atomic amorphous structure and magnetic inhomogeneity on the grain boundaries/surfaces (GBS) [19]. Firstly, with an increase of x value, the crystallization on GBS is improved.…”

“…Nowadays, researchers are focusing on how to obtain a large value of the MR at a low field and room temperature in order to satisfy practical applications. Many attempts have been made to enhance the low field magnetoresistance (LFMR) effect of perovskite manganites by mixture of the CMR materials with secondary phases including insulators [3][4][5][6][7][8], magnetic materials [9][10][11][12][13][14], or metals [14][15][16][17][18][19]. However, the mixture of the CMR material with the insulating grains commonly results in large increase of resistivity and downshift of metal-insulator transition, which limits the practical applications for the circuitmatching requirement.…”

“…There are two reasons: (1) LCSMO is one of the well-studied CMR materials and its T p and T C occur at about 319 K [19]. Usually, the intrinsic MR value in perovskite composites can reach maximum near T C [20], and (2) PdO can be decomposed into metal Pd during the sintering process due to its low decomposition-temperature (∼750 • C) [16].…”

Enhanced Electrical Properties of La $$_{0.7}$$ 0.7 (Ca $$_{0.2}$$ 0.2 Sr $$_{0.1}$$ 0.1 ) MnO $$_{3}$$ 3 Polycrystalline Composites with Ag Addition

“…However, the TCR of LSMO was very low and the T p of LCMO was still below room temperature, which limited the applications of these materials. Therefore, in this direction, based on the high T p of LSMO [5] and large TCR of LCMO [6], preparing La 0.7 (CaSr) 0.3 MnO 3 :Ag x (LCSMO:Ag x ) composites to get the high values of T p and TCR was proposed [14][15][16], and the influence of Ag addition on the electrical properties of LCSMO composites was investigated in this work, which will be helpful to lay the theory and mechanism foundation for further study of manganites with high value of TCR and near room temperature T p .…”