Effects of current on the magnetic states of permalloy nanodiscs

We demonstrate that both the vortex and the single domain magnetic configurations of Ni₈₀Fe₂₀ circular nanodiscs can be achieved by the application of magnetic field or current flowing perpendicular to the disc plane. The magnetic configurations of Ni₈₀Fe₂₀∕Cu∕Ni₈₀Fe₂₀ trilayers have been determined by the response to a small current via the giant magnetoresistance. In addition, we report detection of the vortex state in a single magnetic layer, by exploiting a magnetoresitance arising from the suppression of spin-accumulation in the vortex state. Our analysis shows that this magnetoresistance effect becomes increasingly significant in small nanostructures.