期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 657, 期 -, 页码 495-505出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2015.10.095
关键词
Grain boundaries; Electrical transport; Magnetoresistance; Magnetization; Entropy; Magnetocaloric effect
资金
- Spanish Economy Department [MAT201347231-C2-1-P, MAT2013-48054-C2-2-R]
- Asturias Government [FC-15-GRUPIN14-085]
In this work, we have studied structural, electro-magnetic and magnetocaloric properties of La0.7Ba0.3MnO3/xTiO(2) manganite/insulator system with 0 <= x <= 0.08. X-ray diffraction (XRD) shows the coexistence of TiO2 and La0.7Ba0.3MnO3 phases in doped composites through their characteristic peaks. This reveals their interaction lack preserving the R-3c rhombohedral structure for all composites. Due to interaction lack, TiO2 is suggested to segregate at grain boundaries weakening grains connectivity and decreasing metal-semiconductor transition temperature (T-ms). The segregated TiO2 hinders conduction between grains leading to carriers tunneling that increases the low field magnetoresistance (LFMR) of La0.7Ba0.3MnO3 from -3% to -3.3, -3.5 and -3.7% for x = 0.02, 0.04 and 0.06 for doped composites. The dc magnetization measurements reveal the constant value of Curie temperature (T-c) and its non impact by doping level referring to the TiO2-La0.7Ba0.3MnO3 interaction lack. Also, the magnetocaloric properties of La0.7Ba0.3MnO3 are enhanced with TiO2 doping, where, the relative cooling power (RCP) of La0.7Ba0.3MnO3 has been enhanced from 35 J/kg to 51, 47, 49 and 50 J/kg for x = 0.02, 0.04, 0.06 and 0.08 composites at 1.5T magnetic field. (C) 2015 Elsevier B.V. All rights reserved.
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