Magnetoresistance of Copper-Plated Bismuth Fibers

Abstract

The magnetoresistance of bismuth fibers has been used in our laboratory for measuring magnetic fields at low temperatures. Fibers 2.2 mm long and 25 μ in diameter are quite sensitive and have a very good spatial resolution. It was found that the magnetic field sensitivity of these fibers can be increased by electrolytic copper plating; there is, however, an optimum amount of copper deposited which gives maximum sensitivity. At 14 kG the sensitivity can be increased by about a factor of three from the no-plating case. Magnetic field sensitivities of 1.4 V/A-kG at 14 kG and 4.2°K have been obtained. It has been observed that the response of the copper-plated fibers is quite linear below 1 or 2 kG and above 4 or 5 kG. The low-field sensitivity is several times greater than the sensitivity at 14 kG.