Electrical- Magnetic Transport and Magnetoresistance in La 0.7 Ca 0.3 MnO3/BN Composites
The electrical–magnetic transport properties of (La0.7Ca0.3MnO3)(1-x)/(BN)x composites has been investigated systemically by conventional solid-state reaction method. The results of X-ray diffraction (XRD) and scanning electronic microscopy (SEM) show that BN and LCMO coexist in the composites and BN mainly goes into the grain boundary region without any chemical reaction with La0.7Ca0.3MnO3, which are in accordance with the results of the magnetic measurements. It is very interesting that with increasing of BN content level (x < 0.25), the metal–insulator transition temperature (TP) remains constant (nearly at 275K), and the resistivity increases very slowly. But when x > 0.25, TP shifts to lower temperature and the resistivity increases dramatically. The resistivity threshold of the composites occurred at x = 0.25, and specially the magnetoresistance (MR) reaches a maximum value (about 26.32 %) at 100K in an applied magnetic field of 3kOe. The results also indicate that the doped BN has an important effect on the low field MR (LFMR), which results from spin-polarized tunneling.
Y. D. Zhu et al., "Electrical- Magnetic Transport and Magnetoresistance in La 0.7 Ca 0.3 MnO3/BN Composites", Advanced Materials Research, Vols. 228-229, pp. 379-384, 2011