Effects of current on the magnetic states of permalloy nanodiscs

Abstract

We demonstrate that both the vortex and the single domain magnetic configurations of ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ circular nanodiscs can be achieved by the application of magnetic field or current flowing perpendicular to the disc plane. The magnetic configurations of ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}∕\mathrm{Cu}∕{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ 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.