ISSP - The institute for Solid State Physics

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Sakakibara Group

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Magnetic phenomena in condensed matter can be observed at a wide range of temperatures. In heavy fermions and certain other systems, interesting magnetic behavior often occurs at low temperatures much below 1 K. Because of difficulty in making magnetic measurements at such low temperatures, little work has been done to date. Our interest is to research those magnetic materials having low characteristic temperatures, such as f-electron compounds, heavy fermions, quantum spin systems, and geometrically frustrated spin systems. To study these systems, we also develop necessary equipment. Equipment we have successfully developed includes: high sensitivity magnetometers which are operable even at extremely low temperatures down to the lowest of 30 mK, and equipment to perform angle-resolved specific heat measurements in a rotating magnetic field. The latter is an effective tool for investigating the nodal structures of anisotropic superconductors.

Magnetic phase diagram of the itinerant Ising ferromagnet URhGe. The Curie temperature of this compound can be tuned by applying a magnetic field along the magnetically-hard b axis as shown in the schematic phase diagram (a). A first-order transition appears close to a quantum phase transition region (Hb ~12 T). (b) shows the phase diagram near the quantum phase transition, constructed from the magnetization data. The first-order transition region expands in a wing structure by an additional magnetic field along the magnetically-easy c direction, and closes at a tricritical point (TCP) near 4 K. Quantum wing critical points (QWCP) exist on the T=0 plane.

Research Subjects

  1. Magnetism and superconductivity in heavy electron systems
  2. Multipole orderings and fluctuations in f electron systems
  3. Magnetization of geometrically frustrated magnets
  4. Ground state properties of quantum spin systems