|
Summary of Research Projects (Supports in 2004
Fiscal Year)
| Subjects |
4f Electron Quadrupolar Phase Transition and
Excited State Studied by Neutron and Synchrotron Radiation X-Ray Scattering |
| Representative researcher |
Department of Physics, Tohoku University
Kazuaki IWASA |
| In the field of condensed
matter physics, electron orbital degrees of freedom is a key
issue to understand various physical properties of the strongly
correlated electron systems. We have investigated the multipolar
ordering and the electronic excited states of f electrons
in rare-earth filled skutterudites by neutron and synchrotron
radiation x-ray scattering techniques. It is remarkable that
PrRu4P12 shows thermal evolution of the
crystal-field level splitting of the 4f electrons
of Pr ions below the metal-nonmetal transition at 63 K and
the two inequivalent crystal-field level schemes align periodically
with the Fermi-surface nesting vector. This fact is explained
by a new mechanism of charge density wave formation due to p-f hybridization
giving rise to strong coupling between the antiferro-type ordering
of 4f electron hexadecapole and the spatial modulation
of carrier state originated from the phosphorus p band.
We have also investigated the multipolar ordering below 6.5
K of PrFe4P12 exhibiting the unique heavy-fermion
behaviors. Polarized neutron diffraction experiment revealed
a magnetic-field induced antiferromagnetic component, indicating
the dominant order parameter to be quadrupole O20..
The present results indicate that the 4f electron
multipolar degree of freedom is responsible for the low-temperature
physical properties in PrRu4P12 and PrFe4P12. |
|
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