東北大学 · 物理学・天文学
Johan Åkerman教授の研究室は、スピントロニクスと磁性材料を基盤とし、特に磁性トンネル接合（MTJ）やスピントランスポート型ナノオシレーター（STNO）を用いた次世代メモリデバイスや超高速スピンデバイスの開発を主眼としています。Curie温度の向上や磁性ドロップレットソリトンの発生といった基礎的現象の解明と、それらを応用したIsingマシンやMRAMの信頼性向上にも取り組んでいます。実験的・シミュレーション的アプローチを融合させ、スピンデバイスの高速化・信頼性向上に貢献する研究が進められています。
Figures are computed from collected data and may differ slightly.
Enhancement of Curie temperature of gallium ferrite beyond room temperature by the formation of Ga 0.8 Fe 1.2 O 3 −Y 3 Fe 5 O 12 composite ,
Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation of their magnetic analog has been experimentally challenging. Using spin transfer torque underneath a nanocontact on a magnetic thin film with perpendicular magnetic anisotropy (PMA), we have observed the generation of dissipative magnetic droplet solitons and report on their rich dynamical properties. Micromagnetic simulations identify a wide range of automodulation frequencies, including droplet o
Combinatorial optimization problems are known for being particularly hard to solve on traditional von Neumann architectures. This has led to the development of Ising Machines (IMs) based on quantum annealers and optical and electronic oscillators, demonstrating speed-ups compared to central processing unit (CPU) and graphics processing unit (GPU) algorithms. Spin torque nano-oscillators (STNOs) have shown GHz operating frequency, nanoscale size, and nanosecond turn-on time, which would allow the
The successful commercialization of MRAM will rely on providing customers with a robust and reliable memory product. The intrinsic reliability of magnetoresistive tunnel junction (MTJ) memory bits and the metal interconnect system of MRAM are two areas of great interest due to the new materials involved in this emerging technology. Time dependent dielectric breakdown (TDDB) and resistance drift were the two main failure mechanisms identified for intrinsic memory bit reliability. Results indicate
The bias and temperature dependent resistance and magnetoresistance of magnetic tunnel junctions with and without intentional shorts through the insulating barrier were studied. Based on the experimental results, a set of quality criteria was formulated that enables the identification of barrier shorts. While the temperature and bias dependencies of the junction resistance and of the fitted barrier parameters are very sensitive to the presence of such shorts, the same dependencies of the magneto
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