Perpendicular magnetic anisotropy-based magnetic tunnel junctions(p-MTJs) with low Gilbert damping constant(α) are of particular interest for fast and low-power consumption magnetic random-access memory(MRAM). Howeve...Perpendicular magnetic anisotropy-based magnetic tunnel junctions(p-MTJs) with low Gilbert damping constant(α) are of particular interest for fast and low-power consumption magnetic random-access memory(MRAM). However, obtaining a faster switching speed and lower power consumption is still a big challenge. Herein, we report a Mo-based perpendicular double free layer structure with a low Gilbert damping constant of 0.02 relative to W-based films, as measured by time-resolved magnetooptical Kerr effect equipment. To show the influence of different film structures on the Gilbert damping constant, we measured the Mo-based single free layer. Thereafter, we deposited the full stacks with the Mo-based double free layer and obtained a high tunneling magnetoresistance of 136.3% and high thermal stability. The results of high-resolution transmission electron microscopy(HR-TEM) and energy-dispersive X-ray spectroscopy(EDS) showed that the Mo-based films had better crystallinity,sharper interfaces, and weaker diffusion than the W-based films and thus produced a weaker external contribution of the Gilbert damping constant. As a result of the weak spin-orbit coupling in the Mo-based structure, the intrinsic contribution of the Gilbert damping constant was also weak, thereby leading to the small Gilbert damping constant of the Mo-based stacks. In addition, the macro-spin simulation results demonstrated that the magnetization switching by the spin transfer torque of the Mo-based MTJs was faster than that of the W-based MTJs. These findings help to understand the mechanism behind the good performance of Mo-based p-MTJ films and show the great promise of these structures in low-power consumption MRAM or other spintronic devices.展开更多
One research crucial to wider adoption of Radio Frequency Identification （RFID） technology is how to efficiently transform sequences of RFID readings into meaningful business events. Contrary to traditional events, ...One research crucial to wider adoption of Radio Frequency Identification （RFID） technology is how to efficiently transform sequences of RFID readings into meaningful business events. Contrary to traditional events, RFID readings are usually of high volume and velocity, and have the attributes representing their reading objects, occurrence times and spots. Based on these characteristics and the Non-deterministic Finite Automata （NFA） implementation framework, this paper studies the performance issues of RFID complex event processing and proposes corresponding optimization techniques. Our techniques include： （1） taking advantage of negation events or exclusiveness between events to prune intermediate results, thus reduces memory consumption; （2） with different selectivities of complex events, purposefully reordering the join operations between events to improve overall efficiency, achieve higher stream throughput; （3） utilizing the slot-based or B＋-tree-based approach to optimizing the processing performance with the time window constraint. We present the analytical results of these techniques and validate their effectiveness through experiments.展开更多
基金supported by the National Key R&D Program of China(Grant No.2018YFB0407602)the National Natural Science Foundation of China(Grant Nos.92164206,12104031,11904016,and 61627813)+4 种基金the Science and Technology Major Project of Anhui Province(Grant No.202003a05020050)the International Collaboration Project(Grant No.B16001)the National Key Technology Program of China(Grant No.2017ZX01032101)the Beihang Hefei Innovation Research Institute Project(Grant Nos.BHKX-19-01,and BHKX-19-02)the Guangdong Provincial Department of Science and Technology(Grant No.2020A1515011425)。
文摘Perpendicular magnetic anisotropy-based magnetic tunnel junctions(p-MTJs) with low Gilbert damping constant(α) are of particular interest for fast and low-power consumption magnetic random-access memory(MRAM). However, obtaining a faster switching speed and lower power consumption is still a big challenge. Herein, we report a Mo-based perpendicular double free layer structure with a low Gilbert damping constant of 0.02 relative to W-based films, as measured by time-resolved magnetooptical Kerr effect equipment. To show the influence of different film structures on the Gilbert damping constant, we measured the Mo-based single free layer. Thereafter, we deposited the full stacks with the Mo-based double free layer and obtained a high tunneling magnetoresistance of 136.3% and high thermal stability. The results of high-resolution transmission electron microscopy(HR-TEM) and energy-dispersive X-ray spectroscopy(EDS) showed that the Mo-based films had better crystallinity,sharper interfaces, and weaker diffusion than the W-based films and thus produced a weaker external contribution of the Gilbert damping constant. As a result of the weak spin-orbit coupling in the Mo-based structure, the intrinsic contribution of the Gilbert damping constant was also weak, thereby leading to the small Gilbert damping constant of the Mo-based stacks. In addition, the macro-spin simulation results demonstrated that the magnetization switching by the spin transfer torque of the Mo-based MTJs was faster than that of the W-based MTJs. These findings help to understand the mechanism behind the good performance of Mo-based p-MTJ films and show the great promise of these structures in low-power consumption MRAM or other spintronic devices.
基金supported by the National Natural Science Foundation of China under Grant No.60720106001
文摘One research crucial to wider adoption of Radio Frequency Identification （RFID） technology is how to efficiently transform sequences of RFID readings into meaningful business events. Contrary to traditional events, RFID readings are usually of high volume and velocity, and have the attributes representing their reading objects, occurrence times and spots. Based on these characteristics and the Non-deterministic Finite Automata （NFA） implementation framework, this paper studies the performance issues of RFID complex event processing and proposes corresponding optimization techniques. Our techniques include： （1） taking advantage of negation events or exclusiveness between events to prune intermediate results, thus reduces memory consumption; （2） with different selectivities of complex events, purposefully reordering the join operations between events to improve overall efficiency, achieve higher stream throughput; （3） utilizing the slot-based or B＋-tree-based approach to optimizing the processing performance with the time window constraint. We present the analytical results of these techniques and validate their effectiveness through experiments.
