Data Storage Systems Center

Magnetic annuli, or rings, have the ability to produce various magnetization configurations, which make them attractive for magnetic memory applications [1], [2], [3]. In this study, we present NiFe/CoFe/Cu/CoFe pseudo-spin-valve current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) rings with 600 nm outer diameter and 200 nm inner diameter. It is shown that by directly injecting a vertical current, single-step vortex-vortex magnetic switching is achieved due to contributions from an Oersted field and spin transfer torque [3], [4]. The total contribution of the spin torque and the Oersted field to the switching are separated and quantified, and the mechanisms contributing to the magnitude of each are discussed. Furthermore, it is shown that it is possible to trap a pair of domain walls within the NiFe/CoFe storage layer by initializing the rings with a linear in-plane magnetic field. The presence of the trapped domains leads to a significant decrease in the required switching current, thus enabling a low power switching mode.

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