Giant positive magnetoresistance of Bi nanowire arrays in high magnetic fields

We have studied the magnetoresistance of electrodeposited Bi wires with dia meters between 200 nm and 2 mu m in magnetic fields up to B = 55 T. In zero field, the resistance increases with decreasing temperature, indicating th at the mean free path is strongly influenced by the nanowire geometry. The high-field magnetoresistance shows strong dependence on field orientation; typically 200% for B parallel to the wires, and 600%-800% for B perpendicul ar to the wires. The perpendicular magnetoresistance is well described by a modified two-current model which suggests that the high-field response of the arrays is fairly insensitive to the wire diameter, and is dominated by bulk properties of Bi. (C) 1999 American Institute of Physics. [S0021-8979( 99)69908-X].