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 (ρ) of the composites are largely dependent on Sb2O5 addition level x. TMI shifts downwards and ρ increases with the increase of x at the range of x ≤ 3%, but TMI shifts upwards and ρ decreases with further increasing of x ≥ 3%. The high temperature (T > TMI) semi-conducting part of the ρ 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 3 T 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.