Particle Size Dependence on Magnetic and Electrical Properties of (Ni0.8Fe0.2)10C90 Granular Composites

The granular structure and electrical transport behavior of ball milled magnetic permalloy particles and graphite forming (Ni0.8Fe0.2)(10)C-90 granular composites have been reported. Retaining the composite composition to be 90:10 and varying the particle size of permalloy, the electronic transport properties have been carried out down to 4 K under the external applied magnetic field of 50 kOe. All the samples show semiconducting like behavior and positive magnetoresistance (MR) in the temperature range 4-300 K. A strong anisotropic magnetoresistance in these samples has also been observed. The highest 31% longitudinal and 6.8% transverse magnetoresistance values have been observed in 40 hrs ball milled (Ni0.8Fe0.2)(10)C-90 composite. From these studies, we suggest that the magnetic component present in the sample may not be playing a major role in obtaining large positive MR values, which is in deviation with the earlier reports.