Room-temperature positive magnetoresistance in micro-sized Cox-C1-x composites

Positive magnetoresistance (MR) has been found in Cox-C1-x composites (x=10, 20, 30 and 60 wt%) with an average particle size of 23.5 μm. The composite shows a linear field dependence of the MR at higher magnetic fields (3 T<B<8 T) with no saturation of the MR even at B=8 T at room temperature. Among the Cox-C1-x composites, Co10-C90 has the largest MR value of 58.9% at room temperature with B=8 T and the MR value of 105.6% at a temperature of 5 K with B=5 T. The possible mechanism for the positive MR is discussed