The rapid development of cryogenic computing platforms, including superconducting electronics, quantum information processors, high-performance computing systems, and space applications, has created a demand for memory technologies that operate efficiently, reliably, and scalable at low temperatures. While magnetic random-access memory (MRAM) is a mature and commercially deployed non-volatile memory at room temperature, its behaviour and limitations at cryogenic temperatures remain insufficiently explored, particularly for three-terminal spin-orbit torque magnetic tunnel junctions (SOT-MTJs). This thesis presents a comprehensive experimental and modelling study of SOT-based magnetic memories operated from room temperature (300 K) down to liquid-helium (4 K) temperatures. A dedicated cryogenic characterisation framework is developed to extract magnetic parameters, quantify switching statistics, and evaluate write performance under both quasi-static and sub-nanosecond pulsed conditions. Temperature-dependent measurements reveal enhanced magnetic anisotropy and thermal stability at low temperatures, accompanied by non-trivial trends in critical switching current. By combining experiments with micromagnetic simulations incorporating temperature-dependent material properties and transient Joule heating, this work demonstrates that self-heating remains a dominant factor during write operations, especially at cryogenic bath temperatures. Beyond conventional SOT-MRAM, complementary approaches including optimised spin-transfer torque devices and voltage-gate-assisted SOT switching are investigated. They show that controlling retention via storage layer thickness is a relevant strategy to decrease write current while electric-field control of anisotropy enables efficient modulation of switching across a large temperature range. Overall, this thesis establishes both the physical limitations and technological potential of SOT- and voltage-gated SOT-based MRAM as viable candidates for future cryogenic memory systems.

Plus d'information :https://www.spintec.fr/phd-defense-by-subham-senapati-spin-orbit-torque-based-magnetic-memories-evaluation-for-cryogenic-applications/
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