Giant Positive Magnetoresistance in Grain-Oriented C_xCo_1-x Alloys

The grain-oriented C_xCo_1-x (x = 0.9, 0.5) samples were fabricated by the hot-pressing method. The microstrucre was observed by an x-ray diffractometer and a scanning electron microscope. The resistance against the applied magnetic field was measured by a standard four-point probe method at different temperatures. The magnetoresistance and the magnetization ratio were studied as a function of magnetic field in the range of -1800 kA/m-1800 kA/m at different temperatures from 50 K to 300 K. The magnetoresistance of grain-oriented C_xCo_1-x is positive. The maximum positive MR of 98% at 50 K and 34% at 300 K was obtained under 1800 kA/m magnetic field in the C_0.9Co_0.1 sample.