High-pressure synthesis, electrical and magnetic properties of new filled skutterudites LnOs4P12 (Ln = Eu, Gd, Tb, Dy, Ho, Y)

New filled skutteudites LnOs4P12 (Ln: Eu, Gd, Tb, Dy, Ho and Y) have been prepared at high temperatures and at high pressures. X-ray diffraction of these compounds is studied at room temperature. The relationship between lattice constants and atomic numbers of lanthanide (including Y) is obtained for LnOs4P12 (Ln: lanthanide). Electrical and magnetic properties of the new filled skutterudites with heavier lanthanide have been investigated at low temperatures. EuOs4P12 and GdOs4P12 show ferromagnetic transitions at around 15 and 22 K, respectively. The valence states of both compounds are +2 for the Eu compound and +3 for the Gd compound. DyOs4P12 does not show the magnetic transition down to 2 K. However, a small electrical anomaly is found at around 10 K. YOs4P12 exhibits a superconducting transition at around 3 K. This compound is a new superconductor. Electrical and magnetic anomalies of new filled skutterudites with heavier lanthanide LnOs4P12 (Ln: Eu, Gd, Dy and Y) are discussed. We have also found the electrical anomaly based on the magnetic transition at around 22 K for GdFe4P12.