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With the fast growth of the number of electronic devices on the internet of things (IoT), hardware‐based security primitives such as physically unclonable functions (PUFs) have emerged to overcome the shortcomings of conventional software‐based cryptographic technology. Existing PUFs exploit manufacturing process variations in a semiconductor foundry technology. This results in a static challenge–response behavior, which can present a long‐term security risk. This study shows a reconfigurable PUF based on nanoscale magnetic tunnel junction (MTJ) arrays that uses stochastic dynamics induced by voltage‐controlled magnetic anisotropy (VCMA) for true random bit generation. A total of 100 PUF instances are implemented using 10 ns voltage pulses on a single chip with a 10 × 10 MTJ array. The unipolar nature of the VCMA mechanism is exploited to stabilize the MTJ state and eliminate bit errors during readout. All PUF instances show entropy close to one, inter‐Hamming distance close to 50%, and no bit errors in 104 repeated readout measurements. [ABSTRACT FROM AUTHOR]

We review the recent progress in the development of magnetoelectric RAM (MeRAM) based on electric-field-controlled writing in magnetic tunnel junctions (MTJs). MeRAM uses the tunneling magnetoresistance effect for readout in a two-terminal memory element, similar to other types of magnetic RAM. However, the writing of information is performed by voltage control of magnetic anisotropy (VCMA) at the interface of an MgO tunnel barrier and the CoFeB-based free layer, as opposed to current-controlled (e.g., spin-transfer torque or spin-orbit torque) mechanisms. We present results on voltage-induced switching of MTJs in both resonant (precessional) and thermally activated regimes, which demonstrate fast (<1 ns) and ultralow-power (<40 fJ/bit) write operations at voltages \sim 1.5-2~V . We also discuss the implications of the VCMA-based write mechanism on memory array design, highlighting the possibility of crossbar implementation for high bit density. Results are presented from a 1 kbit MeRAM test array. Endurance and voltage scaling data are presented. The scaling behavior is analyzed, and material-level requirements are discussed for the translation of MeRAM into mainstream memory applications. [ABSTRACT FROM AUTHOR]

In this work, we experimentally study the temperature dependence of the perpendicular magnetic anisotropy (PMA) and of the voltage-controlled magnetic anisotropy (VCMA) in nanoscale MgO|CoFeB|Ta-based magnetic tunnel junctions. We demonstrate that the temperature dependences of both the PMA and the VCMA coefficient follow power laws of the saturation magnetization, but with different exponents. We also find that the linear dependence of the PMA on electric field is maintained over a wide temperature range, although the VCMA strength decreases faster as a function of temperature as compared to the PMA. Possible mechanisms leading to the different exponents are discussed. [ABSTRACT FROM AUTHOR]

Spintronic devices that utilize spin transfer torque are promising for integrated memory applications. However, these devices face substantial energy consumption challenges due to the high current densities required for switching. Conversely, voltage‐driven spintronic devices, using capacitive displacement charge, can realize switching operations that are energy‐efficient (≈1–10 fJ bit−1). This work investigates switching based on voltage control of the interlayer exchange coupling in perpendicular magnetic anisotropy (PMA) multilayered heterostructures. Unlike previous works that utilized gating techniques that employ ionic transport mechanisms to control interlayer exchange coupling, this study employs electrostatic gating by using MgO, which is more compatible with modern spintronic‐based memories. These results suggest that the magnetization anisotropy, and the magnitude, and phase of the Ruderman‐Kittel‐Kasuya‐Yosida (RKKY) coupling function with spacer layer thickness can be controlled through electric gating, providing a promising avenue for the development of energy‐efficient magnetic data storage devices. [ABSTRACT FROM AUTHOR]