Publications by authors named "Ko-ichi Hiraki"
We synthesized two high-pressure polymorphs PbNiO(3) with different structures, a perovskite-type and a LiNbO(3)-type structure, and investigated their formation behavior, detailed structure, structural transformation, thermal stability, valence state of cations, and magnetic and electronic properties. A perovskite-type PbNiO(3) synthesized at 800 °C under a pressure of 3 GPa crystallizes as an orthorhombic GdFeO(3)-type structure with a space group Pnma. The reaction under high pressure was monitored by an in situ energy dispersive X-ray diffraction experiment, which revealed that a perovskit-type phase was formed even at 400 °C under 3 GPa.
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- A study synthesized LiNbO(3)-type MnMO(3) (where M = Ti or Sn) under high pressure and temperature to explore their structures and properties.
- The compounds showed a polar structure and exhibited weak ferromagnetism due to antiferromagnetic interactions at low temperatures (25 K for MnTiO(3) and 50 K for MnSnO(3)).
- There were notable anomalies in dielectric permittivity linked to the ferromagnetic transition temperature, suggesting these materials could be promising candidates for multiferroic applications.
Heat capacity measurements of a charge-ordered organic conductor (DI-DCNQI)2Ag have been performed in a temperature range between 0.3 and 14 K. We found no thermal anomaly at the Néel temperature ( T(N) = 5.
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