Influence of CuO on Electric Transport and Magnetoresistance of La_(0.80)Sr_(0.05)K_(0.15)MnO_3

The two-phase composites of(1-x) La0.80Sr0.05K0.15MnO3/xCuO(x=0.00,0.04,0.08,0.10,0.20,0.30) were prepared by solid-state reaction method.Their structure was detected by X-ray diffraction and scanning electron microscope,and the result indicates that intact perovskite phase and CuO phase are formed,CuO is distributed between perovskite grains,and perovskite grains are surrounded by CuO.Electric transport property and magnetoresistance effect were studied through the measurements of resistivity-temperature(ρ-T) curves in zero field and in applied field,and of magnetoresistance-temperature(MR-T) curves,and the result indicates that the influence of composite CuO on electric transport and magnetoresistance effect of La0.80Sr0.05K0.15MnO3 is very large.Magnetoresistance peak appears in high temperature range,which is the character of intrinsic magnetoresistance;magnetoresistance increases continuously with the decrease of temperature in low temperature range,which is the character of tunneling magnetoresistance induced by grain boundary;the total magnetoresitance is the addition between intrinsic magnetoresistance and tunneling magnetoresistance;the temperature stability of magnetoresistance appears in the intermediate temperature range.