Schematic of a perpendicular DSV with four possible magnetization configurations of the soft layer and first hard layer (hard layer 1), giving rise to a maximum of four distinct resistance states. States B and C in the figure will exhibit the same GMR, provided the MR contributions of each of the two constituent single spin valves are the same, resulting in a three-state system.
GMR curves of a DSV with mismatched spin polarization ratios across two Cu 20 Å spacer layers (lower spin filters , upper spin filters ): (a) major loop (solid line), minor loop 1 with parallel hard layers (dotted with open diamonds) and (b) secondary loop with switching of the lower hard layer (dashed with solid triangles), minor loop 2 with antiparallel hard layers (solid line with crosses). The interfaces with antialigned layers contributing to the GMR are highlighted by thicker lines (colored) in the magnetization state diagrams.
Secondary GMR curves of a well-matched DSV with varying upper spacer layer thicknesses (but fixed ), showing no significant change in the relative GMR contributions from each interface.
Normalized secondary GMR curves demonstrating the achievement of “three-state” and four-state DSV systems with equally spaced resistance levels by tuning spin filter thicknesses at the two spacer layer interfaces. Inset: variation in GMR contributions from each interface with upper spin filter thicknesses, showing variation in only the GMR contribution of the upper interface.
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