Electrical transport and magnetoresistance properties in (1−x)La2/3Ca1/3MnO3/xSb2O5 composites

The composites with the nominal composition of (1-x)La2/3Ca1/3MnO3 (LCMO)/xSb2O5 were fabricated, and their electrical transport and magnetoresistance (MR) behavior were investigated. Experimental results show that the metal-insulator transition temperature (TMI) and resitivity (rho) of the composites are largely dependent on Sb2O5 addition level x. TMI shifts downwards and rho increases with the increase of x at the range of x < =3%, but TMI shifts upwards and rho decreases with further increasing of x > =3%. The high temperature (T > TMI) semi-conducting part of the rho data follow a small polaron hopping (SPH) conduction mechanism, and the metallic behavior of the samples (T < TMI) fits the model in terms of electron-magnon scattering of the carriers. Furthermore, the MR effect can be largely enhanced over a wide temperature range in the composites compared with pure LCMO. At 3T field, the MR rises from a base value 46%, for pure LCMO, to a maximum value of 86.7% for the case of x=3%. It is argued that the enhancement of MR effect is attributed to the enhanced spin-polarized tunneling, which is manipulated by magnetic disorder especially at LCMO grain boundaries caused by Sb2O5 addition.