Evolution of magnetoresistance effect in iron-bismuth films

A unique time-dependent magnetotransport behavior has been observed in Fe-Bi films. Approximately one month was required to stabilize resistance after samples were fabricated. Initially, the as-prepared Fe-Bi films exhibit both ordinary magnetoresistance (MR) and anisotropic magnetoresistance. Fe precipitation changes the microstructure. Eventually, an isotropic and negative MR, like a giant MR effect was observed; it arises from electronic transport between Fe granules separated by Bi.