X-ray absorption spectroscopy and novel electronic properties in heavy fermion compounds YbT2Zn20 (T: Rh and Ir)

YbT2Zn20 (T: Rh and Ir), which crystallizes in the cubic CeCr2Al20-type structure, is a member of the well-known heavy fermion compounds, indicating a huge electronic specific heat coefficient γ ≊ 500 mJ/(K2centerdotmol). We have measured temperature and magnetic field dependences of Yb valence in YbT2Zn20(T: Rh and Ir) at ambient pressure by the Lm edge x- ray absorption spectroscopy in order to investigate the valence state of Yb 4f electrons in these compounds. It is revealed that the Yb valence in both compounds significantly decreases with temperature below about 100 K and increases with increasing magnetic field at low temperatures in contrast to the case of YbCo2Zn20.International Conference on Strongly Correlated Electron Systems 2014 (SCES2014), 7–14 July 2014, Grenoble, Franc

Pressure-volume relationship of a Au-Al-Yb intermediate-valence quasicrystal and its crystalline approximant

正二十面体のAu-Al-Yb準結晶とその1/1近似結晶において室温でおよそ20GPaまでの準静水圧下における放射光X線回折測定を実施した。得られたそれぞれの圧縮曲線は類似しており、圧力に対して単調に減少する。これは高圧力下でこれらが安定であることを示している。得られた体積弾性率は準結晶で105.1(8)GPa、近似結晶で108.1(7)GPaであり、これらの値は基本的に各構成元素の体積弾性率の組成加重平均によって説明される