Large magnetoresistance in Co/Ni/Co ferromagnetic single electron transistors

The authors report on magnetotransport investigations of nanoscaled ferromagnetic Co/Ni/Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2 K. Magnetotransport measurements carried out at 1.8 K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which the authors interpret in terms of a switching mechanism driven by the shape anisotropy of the central wirelike Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which the authors tentatively attribute to excitation of magnons in the central island. (c) 2007 American Institute of Physics.