Multistate storage in dual spin valves with perpendicular magnetic anisotropy

We report the tunable separation of four distinct resistance levels in dual spin valves (DSV) with perpendicular magnetic anisotropy based on Co/Pd and CoFe/Pd multilayers. An optimal giant magnetoresistance (GMR) of 15.2% in the current in-plane geometry was obtained. By varying the spin filter layer thicknesses at the interfaces of one Cu spacer layer from 2 to 6 Å, a linear dependence of GMR across the selected spacer layer was demonstrated without affecting the GMR contribution across the second Cu spacer layer in the DSV. Using this strategy, the intermediate resistance levels in a four-state perpendicular DSV can be adjusted independently, thus creating flexible platform for multistate storage.