About The J-Material Lab

100 micro Kelvin Dilution Fridge

About the group

The group investigates magnetic properties of 4f- and 5f-electron compounds with particular interest in the heavy-electron(heavy-fermion) systems, using very-low-temperature experimental techniques and microscopic measurements such as neutron scattering and muSR. The heavy-electron systems are the inter-metallic compounds which contain elements of the rare earths (Ce, Pr, Yb, etc.) or actinides (U, Np, etc.) and behave as Landau’s Fermi liquids with quasiparticles whose effective masses are two to three orders of magnitudes larger than in ordinary metals. Such electronic states basically result from the hybridization effects that couple the 4f- or 5f- orbital levels of the lanthanide or actinide ions with the conduction states. A blend of this “c-f hybridization” and characteristics of local f orbits in compounds leads to a wide variety of non-trivial aspects of strongly correlated electrons at low temperatures. The heavy-electron compound was first recognized in CeAl3 in 1975 [1], and drew the interests of many physicists by the discovery of superconductivity in CeCu2Si2 four years later [2]. Since then, this research field has been providing a vast amount of new interesting materials and physics, most of which still deserve further investigations. Research on the heavy-electron compounds by our group started 1987, and presently focuses on the issues expressed by the keywords: weak antiferromagnetism, hidden order, anisotropic superconductivity, non-Fermi-liquid behavior, quantum criticality<, quadrupole order, metamagnetism, etc.

[1] K. Andres, J.E. Graebner, and H. R. Ott, Phys. Rev. Lett. 35 (1975) 1979.
[2] F. Steglich, J. Aarts, C.D. Bredl, W. Lieke, D. Meschede, W. Franz, and J. Schafer, Phys. Rev. Lett. 43 (1979) 1892.

Ongoing research

Magnetism and superconductivity of 5f-electron systems
Hidden order and weak antiferromagnetism in URu2Si2
  Anisotropic superconductivity in heavy electron compounds
  Local non-Fermi-liquid behavior in dilute uranium alloys

Magnetism and superconductivity of 4f-electron systems
Magnetism of TmM2Si2 (M: transition metals)
Low-temperature magnetization of non-Fermi-liquid system YbRh2Si2
Low-temperature magnetization of superconducting skutterudite system

Experimental techniques

Crystal growth
Growth of single crystals using tetra-arc furnace
Preparation of polycrystals using plasma-jet furnace

Magnetic, thermal and transport measurements at very low temperature
High precision Faraday-force magnetometer working in mK region
DC magnetization using SQUID magnetometer, AC susceptibility
Specific heat in high magnetic fields
Electric resistivity
Ultrasonic sound verocity

Microscopic measurements
Neutron scattering(ISSP, JAERI)
Muon spin relaxation, rotation and resonance (muSR) (KEK, PSI)

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