Ferro-Antiferromagnetic Coupling and Enhancement of Magnetoresistance in La_0.67Ca_0.33MnO₃/LaMnO₃ Composites

Abstract:

The samples with the nominal composition of (1-x)La0.67Ca0.33MnO3/xLaMnO3 with x=0.00, 0.05, 0.15 and 0.25 were fabricated using a special experimental method. The electrical transport behaviour and magnetoresistance (MR) were studied for the composites in magnetic fields H=0.3T, 3T. Experimental results show that with the increasing LaMnO3 doping level, the metal–insulator（M-I） transition temperature TP shifts to lower temperature and the resistivity increases sharply in zero magnetic field. Meanwhile, a significant enhancement in MR is observed for the composites especially in the low temperature range（below TP）. Specially, the maximum MR at 3 T increased from 35% for the pure La0.67Ca0.33MnO3 to 92% for the sample with x=0.25. We suggest that such enhancement in MR is attributed to the strong ferro-antiferromagnetic coupling effects in the composite system, which increase the magnetic disorder at the grain surface and boundary, will improve the spin-polarized tunneling process of the conducting electron between adjacent grains, and thus enhance the MR effects.

• Periodical: Advanced Materials Research (Volume 662)
• Pages: 485-489
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.662.485
• Online since: February 2013
• Authors: Guang Ming Ren, Jing Lin Liu
• Keywords: Composite Granular System, Ferro-Antiferromagnetic Coupling, Magnetoresistance, Perovskite Manganite Oxides, Spin-Polarized Tunneling

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