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In the field of information hardware security, random variations obtained during device manufacturing process play a key role in generating unique and unclonable security keys. Existing physical unclonable functions (PUFs) utilizing these static randomnesses usually exhibit static challenge‐response pairs, which cannot be refreshed and limit their application prospects. Here, it is demonstrated that purely electrical controllable spin–orbit torque (SOT)‐based reconfigurable PUFs (rPUFs) can be realized in Pt/IrMn/Co/Ru/CoPt heterojunctions. By applying current pulses along two orthogonal directions, both the exchange bias between IrMn and Co and the SOT switching polarity (clockwise or counterclockwise) of perpendicularly magnetized CoPt can be reversibly controlled, which enables the realization of four rPUF states within a single device. By taking advantages of the sample growth and micro‐nanofabrication induced variations in the critical switching current density of SOT‐driven magnetization switching, the rPUF device with relatively good uniqueness and low bit error rate is achieved. Our work provides an approach to information hardware security and broadens the application of spintronics. [ABSTRACT FROM AUTHOR]

Flexible synaptic devices that emulate biological synapses are the key to developing wearable intelligent equipment. However, there are still challenges to achieving multiple synaptic functions in flexible synaptic devices and realizing large‐scale production of synaptic devices. Herein, a flexible synaptic transistor on polyimide substrate is designed and fabricated using a solid‐state electrolyte gate and a VO2 Mott insulator thin film channel. Four orders conductance modulation is obtained in the VO2 thin film channel across the metal‐insulator transition. Several essential synaptic behaviors, including potentiation, depression, and short‐term/long‐term plasticity, are successfully demonstrated in this flexible synaptic device. More importantly, this synaptic transistor exhibits high cycling stability and good tolerance to bending deformation. A simulated artificial neural network built from this synaptic device achieves high recognition accuracy of 98% in the flat state and 92% in the bending state. In addition, this flexible device is fabricated on polyimide substrate by magnetron sputtering method, which has low cost and is compatible with modern semiconductor technology. This work can pave the way for large‐scale production of flexible synaptic Mott transistor devices. [ABSTRACT FROM AUTHOR]

Voltage‐driven oxygen ion migration in ferromagnetic metal/oxide heterostructures offers a highly effective means to tailor emergent interfacial functionalities. In heterojunctions with a core structure of Pt/Co/CoO/TiO2 (TaOx), it is demonstrated that exchange coupling of magnetic moments across the Co/CoO interface provides an extra source to stabilize the perpendicular magnetic anisotropy (PMA). Moreover, the strength of this interfacial coupling can be reversibly controlled through voltage‐driven oxygen ion migration at the Co/CoO interface, resulting in electrical‐field‐controllable PMA. In combination with the spin current generated from Pt, it is revealed that the spin‐orbit torque (SOT) switching of the perpendicular magnetization of Co can be turned ON/OFF by electrical field. Tunable PMA and SOT switching makes heavy metal/ferromagnetic metal/antiferromagnetic oxide heterojunctions a promising candidate to future voltage‐controlled, ultralow‐power, and high‐density spintronics devices. [ABSTRACT FROM AUTHOR]

Spintronics: Electrical Control of Perpendicular Magnetic Anisotropy and Spin-Orbit Torque-Induced Magnetization Switching (Adv. In article number 1900782, Yufeng Tian and co-workers demonstrate that exchange coupling of magnetic moments across the Co/CoO interface provides an extra source of stabilization for the perpendicular magnetic anisotropy (PMA) in heterojunctions with a core structure of Pt/Co/CoO/TiO2 (TaOx). The inside cover image shows a representation of this system, with the background showing a Pt/Co/CoO/oxide/Pt cell crossbar array on a chip and the center showing an enlarged view. [Extracted from the article]