Tuning Damping and Magnetic Anisotropy in Ultrathin Boron‐Engineered MgO/Co–Fe–B/MgO Heterostructures

Abstract Nanometer‐thick Co–Fe–B/MgO based structures have been widely accepted as the preferred system for immediate and long‐term goals in magnetic random access memory (MRAM) devices because of excellent spin‐torque efficiency and promise for high‐density MRAM. To realize next‐generation ultra‐low‐power MRAM, further lowering of power consumption in these structures is a crucial ongoing effort. Gilbert damping is one critical material parameter toward lowering energy consumption but is traditionally large (≈10 −2 ) in these Co–Fe–B/MgO systems. Here, Gilbert damping of (1.3 ± 0.3) × 10 −3 from a perpendicular double Co–Fe–B/MgO interface system engineered at different boron compositions is reported. Remarkably, this value is achieved with ≈1 nm of Co–Fe–B thickness while maintaining magnetic anisotropy of 0.4 Merg cc −1 . An unusual damping trend that scales with layer thickness in high‐boron content films established from both experiments and first‐principles calculations is reported.