CoIr/Pt Multilayers Enabling Physical Unclonable Function via Domain Wall Motion.

Spintronics devices offer exceptional long-term reliability and compatibility with complementary metal-oxide semiconductors, making them promising for next-generation electronics. However, realizing their full potential requires new materials and device concepts that operate at low energy. In this work, we introduce a CoIr/Pt heterostructure that leverages the properties of CoIr, which exhibits negative magnetocrystalline anisotropy. By interfacing CoIr with Pt layers, we successfully invert its anisotropy, achieving a perpendicular magnetization with a low effective magnetic anisotropy energy. The stack shows a switching current density five times lower than that of conventional Co/Pt stacks. We use this material in a physically unclonable function (PUF) domain wall (DW) device that generates unique cryptographic keys. Unlike conventional DW devices, which struggle to generate distinct states due to challenges in controlling DW motion in straight wires, our CoIr/Pt stack enables a 4 × 32-bit PUF without pinning sites, allowing for simplified programming architecture. Distinctive outputs are demonstrated in spin-orbit torque-driven 4 × 32-bit PUF devices. Additionally, this stack facilitates PUF miniaturization to the nanoscale, enhancing device density and power efficiency. Our results present a promising approach to hardware security primitives, offering potential integration into secure electronic systems.