Fast current-driven switching of magnetic vortex states in permalloy microrings

We report on the use of current pulses as short as 70 ns to control the chirality of microscale vortex magnetic rings. D-shaped permalloy rings were deposited on oxidized silicon and a central via was etched through the oxide to the wafer below. Current was supplied through an evaporated gold contact overlying the narrow control portion of the D-ring and grounded through the via. Magnetization states were read out optically using the longitudinal magneto-optic Kerr effect and an antireflection coating that breaks the symmetry of the vortex magnetization signal. Sub-nanojoule switching energies are dominated by resistive losses in the leads. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4799657]