Electrical transport properties and enhanced broad-temperature-range low field magnetoresistance in LCMO ceramics by Sm2O3 adding

• Published in: Journal of alloys and compounds 2019-06, Vol.790, p.240-247
• Main Authors: Li, Junfeng, Chen, Qingming, Yang, Sheng'an, Yan, Kaikai, Zhang, Hui, Liu, Xiang
• Format: Article
• Language: English
• Subjects: Ceramics; Composite materials; Composite structures; Diffraction patterns; Electron microscopes; Emission analysis; Field emission microscopy; Grain boundaries; Insulator-metal (I-M) transition; La0.67Ca0.33MnO3/mol%(Sm2O3)x (LCMO/(SO)x) ceramics composites; Lattice parameters; Low-field magnetoresistance; Magnetic properties; Magnetoresistance; Magnetoresistivity; Sol-gel processes; Temperature dependence; Transport properties; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2019.03.169

Polycrystalline La0.67Ca0.33MnO3 (LCMO) ceramics were prepared by the sol-gel method. LCMO/mol%(Sm2O3)x (LCMO/(SO)x, x = 0, 0.01, 0.03, 0.05, 0.10) ceramics composites were synthesized using solid state sintering. Effects of Sm2O3-adding on the structures, electrical transport and magnetoresistance properties of the as-prepared LCMO/(SO)x samples were studied. The refinement of the X-ray diffraction (XRD) patterns showed that the lattice parameters (a, b, c, V) of LCMO are slightly decreased, indicating Sm3+ ion substitution of A-site rose. Field emission scanning electron microscope (FE-SEM) study confirmed the composite structure of LCMO/(SO)x ceramics samples. At x ≤ 0.03, the temperature dependence of resistivity shows a double insulator-metal (I-M) transition. While at x ≥ 0.05, it exhibits a single I-M transition with broad transition width at low temperature. An interesting and important result for the present LCMO/(SO)x ceramics composites is the observation of the enhanced transversal low-field magnetoresistance (LFMR) at low applied magnetic field of 300 and 500 mT over a broad temperature range of below ∼ 260 K. •Two insulator-metal transitions were observed in La0.67Ca0.33MnO3-Sm2O3 composites.•Low-field magnetoresistance (LFMR) was enhanced over a wide temperature range.•The broad temperature range of LFMR is ascribed to the high grain boundary ratio.•More efficient dispersal of Sm2O3 at grain boundary leads to the increase in LFMR.