Abstract: A composite granular system consisting of La_2/3Ca_1/3MnO₃ 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 La_2/3Ca_1/3MnO₃. The pure La_2/3Ca_1/3MnO₃ 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.

Key words: ferromagnetic metallic granular system, spin-polarized tunneling, low-field magnetoresistance, colossal magnetoresistance