Emergent Spin Structure Research Unit

Principal Investigator

PI Name Taro Nakajima
Degree D.Sci.
Title Unit Leader
Brief Resume
2010Ph.D., Tokyo university of Science
2010Research Associate, Department of Physics, Faculty of Science, Tokyo University of Science
2014Postdoctoral Researcher, Strong Correlation Quantum Structure Research Team, RIKEN Center for Emergent Matter Science.
2016Research Scientist, Strong Correlation Quantum Structure Research Team, RIKEN Center for Emergent Matter Science
2019Project Associate Professor, Quantum-Phase Electronics Center, The University of Tokyo (-present)
2019Unit Leader, Emergent spin structure research unit, RIKEN Center for Emergent Matter Science (-present)

Outline

In strongly correlated electron spin systems, symmetry of magnetic structure may play important role to induce emergent phenomena such as spin-driven ferroelectricity in multiferroics and topological Hall effect in magnetic skyrmion systems. We study these phenomena by means of neutron and synchrotron radiation x-ray scattering, which are powerful tools to reveal the magnetic structures, their collective excitations and fluctuations. We also develop new techniques in neutron and x-ray scattering to resolve (temporal) changes in magnetic structure under extreme conditions, for example, application of electric current and anisotropic stress.

Research Fields

Physics

Keywords

Multiferroics
Magnetic skyrmions
Neutron scattering
Synchrotron radiation x-ray scattering

Results

Stroboscopic small-angle neutron scattering on the skyrmion lattice state in MnSi

Magnetic skyrmions are nanometer-scale magnetic vortices, which often appear as a field-induced state in a long-wavelength helimagnet. They have attracted much interest because their topologically nontrivial spin texture endows each skyrmion with robust stability and particle nature. We investigated the phase-transition kinetics of magnetic skyrmion lattice (SkL) in an archetypal skyrmion compound MnSi. In a thermoequilibrium condition, the SkL appear only in a narrow window of temperature near the critical temperature. However, it was recently revealed that a metastable skyrmion state is realized at low temperatures by rapidly cooling the sample under magnetic field. To reveal the phase-transition kinetics during the rapid cooling, we performed stroboscopic SANS measurements with time resolution of 13 ms while sweeping temperature as fast as 50 Ks-1. We successfully observed that a hexagonal diffraction pattern, which is the hallmark of the triangular SkL, evolving with temperature and that the SkL survives down to low temperatures upon rapid cooling.

A schematic illustration of the stroboscopic SANS measurement.

Members

Taro Nakajima

Unit Leader taro.nakajima[at]riken.jp R

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