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Otani Group

Research Associate

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The concept of spin current, a flow of spin angular momentum, appeared in the end of 20th century, and evolved a new spintronic principle based on the atomic-scale angular momentum conservation such as spin-transfer-torque. The methods to generate, transport and detect the spin currents have been well established in the following decade, leading the spintronics research to a new phase. Recent studies revealed interconversions among quasi-particles such as electron, spin, phonon, photon and magnon etc. via spin current in a solid. These interconversions, called as “spin conversion”, often take place in the nano-scale regions at the interfaces of deferent materials, and thus, have great versatility and application possibility. Our fundamental researches explore new processes of the spin conversion and clarify their mechanisms. We also develop the spintronics devices to control a variety of spin conversion processes using nanofabrication technologies.

The relation between the conversion efficiency of spin Hall effect and the conductivity. (a) The schematic of spin absorption method. The pure spin current generated by the current flows between Cu and Py electrodes, diffuses to right direction through the spin transport channel (Cu). The spin current is absorbed by the spin Hall material (Pt), and converted to charge current via inverse spin Hall effect. (b) The field dependence of inverse spin Hall resistance (RISHE = V/I) of Pt. (c) The conductivity dependence of spin Hall angle (spin-current conversion efficiency))θSH of Pt. There has been a significant spread in the θSH of Pt among reports. We revealed that the θSH depends on the conductivity: the film quality of Pt, and the dependence can be explained extrinsic and intrinsic mechanisms.
Spin-to-charge current conversion by inverse Rashba-Edelstein effect. (a) Fermi contours splitting by Rashba effect and the shift of Fermi surface to perpendicular direction of spin polarization induced by non-equilibrium spin accumulation after spin injection. (b) Schematic image of the experimental setup for spin-current conversion at the interface of Cu/Bi2O3. (c) Magnetic field dependence of the inverse Rashba-Edelstein voltage by means of spin pumping.

Research Subjects

  1. Mechanisms of pure spin current generation and detection
  2. Magnetic phase transition by using spin current
  3. Spin-to-charge current conversion in the interface of topological insulator
  4. Spin injection into organic materials
  5. Spin injection into superconductor from ferromagnet