ISSP - The institute for Solid State Physics

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Nakajima Group
Associate Professor

Research Associate

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Magnetism in solids has been extensively studied in the field of condensed matter physics for a long time. A well-known example is ferromagnetism, which means that magnetic moments in a solid are spontaneously aligned to be parallel to each other owing to exchange interactions. It was recently revealed that spontaneous ordering of the magnetic moments can change not only magnetic properties of the system, but also (di)electric or elastic properties. We study the emergent cross-correlated phenomena induced by the spin orders. One example is spin-driven ferroelectricity, where a spiral magnetic order breaks spatial inversion symmetry of the system and leads to spontaneous electric polarization. Another example is a vortex-like spin texture called magnetic skyrmiom, which often appears in a long-wavelength helimagnet. By the virtue of the topologically-nontrivial spin texture, the magnetic skyrmion induces an effective magnetic field acting only on conduction electrons.

(a) A schematic of magnetic skyrmion lattice. (b) The equilibrium and metastable state diagram of MnSi. The metastable skyrmion lattice state is realized by a rapid temperature sweep in a magnetic field of 0.2 T.
The results of time-resolved neutron scattering measurement on MnSi in a magnetic field; the hexagonal diffraction patterns correspond to a triangular lattice of metastable skyrmions.

Research Subjects

  1. Neutron scattering studies on magnetic skyrmions and their dynamics
  2. Magnetic excitations driven by the electric field component of light – electromagnons -
  3. Control of magnetic and dielectric properties in multiferroics by means of anisotropic stress
  4. Time-resolved neutron scattering studies on nonequilibrium and transient phenomena