Tohoku University · Physics and Astronomy
Professor Johan Åkerman's research lab specializes in spintronics and nanomagnetic materials, focusing on the development of advanced magnetic materials and devices for next-generation computing and memory technologies. Key research directions include the engineering of magnetic oxides with enhanced Curie temperatures, the exploration of dissipative magnetic solitons in nanostructured systems, and the application of spin torque nano-oscillators in ultrafast Ising machines for combinatorial optimization. The lab also investigates the reliability and failure mechanisms in magnetic random-access memory (MRAM), particularly concerning tunnel junctions and interconnect systems, aiming to enable robust commercialization of spintronic devices.
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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