Pressure-induced formation of intermediate-valence quasicrystalline system in a Cd-Mg-Yb alloy

Cd-Mg-Yb準結晶合金の加圧による中間価数準周期系の形成

綿貫 徹; 川名 大地*; 町田 晃彦; Tsai, A. P.*

Watanuki, Tetsu; Kawana, Daichi*; Machida, Akihiko; Tsai, A. P.*

Cd-Mg-Yb正20面体型準結晶を加圧することにより、中間価数準周期系を作製した。Yb-吸収端近傍のX線吸収実験で高圧下のYb価数評価を行ったところ、Yb価数は圧力とともに増加し、常圧で2価のYbが57.6GPaでは2.71価をとることが明らかとなった。周期Yb系では2.7価付近以上で電子質量が異常に増大を見せる強相関領域であり、準結晶でも同領域に到達した系ができているものと考えられる。

A quasiperiodic intermediate-valence system was prepared by applying pressure to an icosahedral Cd-Mg-Yb quasicrystal. X-ray absorption spectroscopy near the Yb -edge demonstrates that the Yb valence increases continuously upon compression from the divalent state (4) at ambient pressure and reaches a value of 2.71 at 57.6 GPa, which is close to the trivalent state (4). By following the trend of Yb-based intermediate-valence crystalline compounds, this large valence increase suggests the change of 4 character in the Cd-Mg-Yb quasicrystal from an itinerant state with weak electron correlations to an intermediate region between an itinerant and a localized state with strong correlations.