Research Institute of Electrical Communication Tohoku University

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Masafumi Shirai,Professor

Kazutaka Abe,Associate Professor

Masahito Tsujikawa,Assistant Professor

K.Abe M.Shirai M.Tsujikawa

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Research Activities

Various kinds of materials are utilized for processing, communication, and storage of massive data in modern information devices. Our research objectives are as follows: (1) theoretical analyses of quantum phenomena in materials and nanostructures, (2) computational design of materials and nanostructures which possess new functionalities, (3) development of materials design scheme utilizing large-scale computational simulation techniques.

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Materials Functionality Design (Prof. Shirai)

Our research interest is focused on “spintronics” to realize new functional devices. The main topic is theoretical analysis of spin-dependent transport properties in highly spin-polarized materials. We extend our theoretical research to electric-field effect on magnetic anisotropy in ferromagnetic films for realizing low power- consumption devices.
The giant magnetoresistive devices using half-metallic Heusler alloys are promising for application to the read-out head of hard disc drives. We theoretically design non-magnetic materials for a spacer layer between two ferromagnetic layers. We found that the Fermi-surface matching between the Heusler alloy and Ag3Mg ordered alloy is better than Ag. Experimental results confirm the improved magnetoresistance for the device using the Ag3Mg spacer. [ T. Kubota, et al., J. Phys. D: Appl. Phys. 50, 014004 (2017). ]

Research topics

  • Design of new spintronics materials based on first-principles calculation
  • Theoretical analysis of transport properties in spintronics devices
  • Computational simulation of nanostructure-growth process on surface
  • Development of simulation scheme for material/device functionality design

Materials Science under Extreme Conditions(Assoc. Prof. Abe)

We investigate the properties of dense materials by using ab initio methods. Our current research focuses on metallic hydrides, which are predicted to show high-temperature superconductivity driven by electron-phonon coupling. We are also developing simulation techniques to search stable structures from first principles. The structural search methods are quite useful for examining unknown substances and, therefore, likewise applicable to designing new materials at one atmosphere.

Research topics

  • Matter at high densities.
  • Metallization and superconductivity of hydrogen and hydrides.
  • Development of first-principles structural search methods.

Fig.1:The dependence on in-plane wavevector of the majority-spin channel conductance calcuated for Co2(Fe,Mn)Si/Ag/Co2(Fe,Mn)Si (left) and Co2(Fe,Mn)Si/Ag3Mg/Co2(Fe,Mn)Si (right) junctions [taken from T. Kubota, et al., J. Phys. D: Appl. Phys. 50, 014004 (2017).]