Structural properties of Y_1–xYb_xNi₂B₂C synthesized at high pressure: EXAFS data analysis

Local structure of Y_1–xYb_xNi₂B₂C 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 Einstein temperature Θ_E = 350 K, while a minimum value of Θ_E = 300 K is reached for the compound with x = 0.025, which has the highest critical temperature T_c = 12.5 K of the superconductive transition. This correlates with the further suppressing of superconductivity and with the appearance of the local magnetic moments in the investigated Y_1–xYb_xNi₂B₂C series for x ≥ 0.05 compounds. Observed changes in the local electronic and the local crystal structure of this system as a function of Yb concentration and of temperaturre were explained in the frame of the band filling effect.