Reconfigurable optical physical unclonable functions based on voltage-controlled magnetic anisotropy

Physical unclonable functions (PUFs) generate secure cryptographic keys by harnessing the intrinsic hardware randomness, offering enhanced robustness against adversarial attacks. Spintronic devices have been incorporated into PUFs by exploiting the stochastic distribution of magnetic properties, such as magnetic anisotropies or switching currents. Here, we demonstrate a reconfigurable spintronic optical PUF based on voltage-controlled magnetic anisotropy (VCMA) in heavy metal/ferromagnet/oxide structures with an HfO2 gate oxide. In these structures, when the magnetic anisotropy is switched from in-plane to perpendicular through the VCMA effect, randomly distributed magnetic domains with perpendicular magnetization emerge and are optically detected using magneto-optical Kerr microscopy. These domain patterns serve as an entropy source for security keys, exhibiting desirable PUF characteristics, including randomness, uniqueness, and a large encoding capacity. Furthermore, we show that the domain patterns can be regenerated by repeatedly applying gate voltages, enabling the electrical reconfigurability of our PUFs. Our work provides a novel approach to realizing electrically reconfigurable optical PUFs based on spintronic devices.