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Takeyama Group

Research Associate

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We are engaged in development for generating ultra-high magnetic fields above 100 T, and pursue the solid-state science realized under such an extreme condition. We employ two methods for the ultra-high magnetic field generation, one is the electro-magnetic flux compression (EMFC) and the other is the single-turn coil (STC) method. We have established a new type of coil for the EMFC, and currently the maximum magnetic field is 730 T. This value is the highest achieved thus far in an indoor setting in the world. Further development is underway for achieving much higher fields, more precise and reliable measurements for the solid-state physics. We are now involved in construction of ultra-high magnetic field generator system under the 1000 T project. The horizontal and vertical (H- and V-) STCs are used for more precise measurements up to 300 T, respectively, in accordance with their magnetic field axes. The H-STC is mainly used for magneto-optical measurements by use of laser optics, whilst the V-STC is more suitable for the study of low-temperature magnetization in a cryogenic bath. We are conducting the studies on magneto-optics of carbon nano-materials or of semiconductor nano-structures as well as on the critical magnetic fields in superconducting materials and on the high-field magnetization processes of the magnetic materials with highly frustrated quantum spin systems.

Newly-developed ultra-high magnetic field generator of the electro-magnetic flux compression method. The 5MJ fast condenser bank is capable of supplying maximum electrical current of amount to 8 mega-ampere, which is injected to a primary coil through the collector plate. By upgrading the performance such as the maximum charging voltage and the residual impedance, ultra-high magnetic fields up to 1000 T are planned to generate.
High magnetic field magnetization of Volborthite measured by Faraday rotation in magnetic field up to 180 T at temperature 5 K. Ultra-high magnetic fields are generated by a single-turn coil magagauss generator. Volborthite (Cu3V2O7(OH)2・2H2O) is a spin 1/2 kagome frustrated antiferromagnet. Left upper inset depicts an experimental set-up of a high-angle resolution Faraday rotation optical alignment and a miniature size liquid He flow type optical cryostat which is totally made of glass epoxy. A picture right down is a Volborthite sample, both sides of which are polished to the optical flat. There observed a jump to 1/3 magnetic plateau at 26 T and the plateau continues up to around 103-112 T, then gradually grows until saturation nearly at 180 T.

Research Subjects

  1. Technical developments for ultra-high magnetic field magnets above 100 T and for solid-state physics measurements
  2. Magneto-optics in ultra-high magnetic fields
  3. Magnetization processes of magnetic materials and the critical magnetic field in superconducting materials in ultra-high magnetic fields