Large Magnetoresistance under a Low Applied Magnetic Field in a Cu-dependent Material Coated-La_(2/3)Ca_(1/3)MnO_3 Granular System

A composite granular system consisting of La2/3Ca1/3MnO3 grains and Cu-dependent material, introduced into the boundary region of the granular surface, was fabricated in a chemical route. The measurement of magnetoresistance versus temperature dependence for a low magnetic field (0.3 T) indicates that the features of magnetoresistance in the composite granular system are significantly different from that in pure La2/3Ca1/3MnO3. The pure La2/3Ca1/3MnO3 granular system shows a monotonic increasing response in magnetoresistance with cooling. But for the composite granular system, a sharp peak with large magnetoresistance appears in the magnetoresistance versus temperature curve at a temperature near which the insulator-metal transition occurs. The experimental observation was discussed based on the measurement of low-field magnetization.