Anomalous Magnetoresistance of Speer Carbon Resistors at Low Temperatures

Abstract

Magnetoresistance of Speer carbon resistors has been measured in the Temperature range 0.05–4.2 K and in magnetic fields up to 84 kOe. Both negative and positive magnetoresistances (MR) have been observed. The negative MR becomes large with decreasing temperature and is proportional to H 1/2 in weak magnetic fields below about 17 kOe and saturates in higher magnetic fields. On the other hand, the positive MR is notable in high magnetic fields and in the temperature range around 1 K. These results are discussed with recent theories of the Anderson localization.