Structural properties of Y1-xYbxNi2B2C synthesized at high pressure: EXAFSdata analysis

Local structure of Y1-xYbxNi2B2C series synthesized at high pressure 8 GPa has been studied using EXAFS. Measurements were performed at the Ni K-edge in temperature range 5-300 K. The results show that the Debye-Waller factor for Ni-Ni bond in the parent YNi2B2C compound is characterized by the Eins tein temperature Theta (E) = 350 K, while a minimum value Theta (E) = 300K is reached for the compound with x = 0.025, which has the highest critical temperature T-c = 12.5K of the superconductive transition. This correlates with the further suppressing of superconductivity and with the appearance o f the local magnetic moments in the investigated Y1-xYbxNi2B2C series for x greater than or equal to 0.05 compounds. Observed changes in the local ele ctronic and the local crystal structure of this system as a function of Yb concentration and of temperature were explained in the frame of the band fi lling effect.