Enabling high giant magnetoresistance in simple spin valves with ultrathin seed and free layers

Emerging spin–orbit torque devices based on spin valves require a thin magnetic free layer to maximize the torque per moment. However, reducing the free-layer thickness to ≲2 nm deteriorates the giant magnetoresistance (GMR) signal for electrical readout. Here, we demonstrate that the addition of a 1 nm Cu seed layer promotes sharp interfaces in simple polycrystalline Co-based spin valves, enabling high GMR ratios of 5%–7% at sub-2 nm free-layer thicknesses. Our work offers a pathway for engineering high-signal GMR readout in spin–orbit torque digital memories and neuromorphic computers.