Magnetoresistance of Bismuth in Bulk and Thin Film Forms

A comparative study of the room temperature magnetoresistance (MR) of bulk polycrystalline Bi and its thin film formulations by thermal evaporation is made. The magnetoresistance value for the bulk Bi is found to be positive, reaching a value of 110% in fields of 2T in agreement with the previously reported values. The thermally evaporated thin films of thickness 100 - 300nm show a crystalline nature and the MR values are in the range 3-10%. The resistivity of the thin films shows a semiconducting behavior with a negative temperature coefficient resistance (TCR). Annealing the samples in temperatures of 200 degrees C (below the melting point of pure Bi) is found to cause a reduction in magnetoresistance in thin film samples while there is not much change in the bulk.