Electrical Transport and Giant Magnetoresistance in (1 - x) La 0.67 Ca 0.33 MnO 3/ x CuO Composites

Abstract

Samples with nominal composition of (1 - x) La 0.67Ca 0.33MnO 3 (LCMO)/xCuO ( x = 0%, 2%, 4% and 20%) were made using a special experimental method. The temperature dependence of the resistivity (ρ) of the composites was investigated in the temperature range of 10 ∼ 300 K and different magnetic fields of H = 0, 0.1, 0.3, 0.5. 1.0 and 3.0 T. The results showed that CuO percentage x had important effects on metal-insulator transition temperature ( T p), zero field peak resistivity (ρ max), and magnetoresistance ( MR) properties of the composites. T P shifted sharply towards low temperature with the increase of x in the range of x ≤ 4%, but was almost independent of x at high level of CuO content. Composites with x = 4% and 20% exhibited similar electrical transmission behavior. Compared with pure LCMO, enhanced magnetoresistance could be clearly observed even in a quite low magnetic field of 0.3 T. For x = 4% and 20% samples, the MR value at 0.3 T could reach as high as ∼ 88% and ∼ 90%, respectively. XRD and SEM analysis showed that the substantial enhancement of MR, especially near T p, was because of local spin disorder between contiguous LCMO ferromagnetic particles caused by the addition of CuO.