Osaka Prefecture University

Demonstrating 2D Melting Phenomena in a Magnetic System

LastUpDate: January 17, 2019

Prof. Yoshihiko Togawa, Osaka Prefecture University, Prof. Jun-ichiro Kishine, The Open University of Japan, and their collaborators have succeeded to demonstrate a universal hierarchy of 2D melting phenomena in a magnetic system for the first time. Their results shed light on the long standing issue discussed among the material science community since the famous theoretical proposal by Kosterlitz, Thouless, Halperin, Nelson, and Young (KTHNY) in 1970s.

Their results have been published in ‘Physical Review Letters’ journal issued by American Physical Society on 9th January 2019.

Title of article “Anomalous Temperature Behavior of the Chiral Spin Helix in CrNb3S6 Thin Lamellae”

The main point of research

  • Figure: Schematic picture of 2D melting phenomena in a magnetic system, image

    Figure: Schematic picture of 2D melting phenomena in a magnetic system

    They succeeded to demonstrate the KTNHY theory in thin-film lamellae of the prototype monoaxial chiral helimagnet( *1) CrNb3S6 with so called chiral symmetry breaking( *2), which means breaking of left-right symmetry, and exhibit a universal hierarchy of 2D melting phenomena.
  • They examined the periodicity of a chiral helimagnetic order (CHM) and observed how the magnetic order melts in CrNb3S6 thin films.
  • Their experimental findings were consistently explained using theoretical framework called “field theory and renormalization”.
  • Their results make an impact on the material science community with the first experimental demonstration of the KTHNY theory in a magnetic system.


*1 Chiral helimagnetic material

A chiral helimagnetic material is a magnetic crystal which has the structure without left-right (chiral) symmetry. In this class of materials, magnetic spins exhibit a helical spin arrangement in which spins rotate along the crystal axis with a fixed rotational direction.

*2 Symmetry breaking

When a magnetic material is cooled down below the magnetic phase transition temperature, it exhibits a magnetic order with electron spins being regularly arranged over the whole material. This long-range ordered state is regarded as a state with low symmetry. On the other hand, the orientations of electron spins become random above the phase transition temperature, which corresponds to a state with high symmetry. Namely, the phase transition from high to low symmetry states are a consequence of a spontaneous symmetry breaking.

Research Grant

The research was supported by JSPS Grant-in-Aid for Scientific Research (B) (JP17H02767, JP17H02923).


Department of Electronics and Physics, Graduate School of Engineering, Osaka Prefecture University

Prof. Yoshihiko Togawa

Email y-togawa[at] *Please change [at] to @.

Faculty of Liberal Arts, The Open University of Japan
Prof. Jun-ichiro Kishine

Email kishine[at] *Please change [at] to @.