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 cell for transport measurements under high pressure and low temperature in pulsed magnetic fields

International audienceWe present a new specially designed pressure cell and technique adapted for resistivity measurements in pulsed magnetic fields up to 60 T at pressures up to at least 4 GPa, and temperatures down to 1.5 K. We show that heating effects during the pulse are acceptable (less than 1 K) and can be corrected allowing reliable temperature dependences of the magnetoresistance to be obtained. We illustrate the performance with a study of the phase diagram of the heavy fermion antiferromagnet CeRh2Si2

Large Cyclotron Effective Mass Detected by de Haas-van Alphen Effect in YbCu2Si2

International audienceDe Haas-van Alphen experiments were performed on the valence fluctuation compound YbCu2Si2. For the field direction close to the c-axis in the tetragonal structure, a very large cyclotron effective mass of 43m(0) was detected on branch beta, which corresponds to the nearly cylindrical Fermi surface. This mass is one of the largest cyclotron masses detected experimentally in Yb compounds