L.N. Fomicheva

Hall-Effect study of YNi2B2C superconductor

Hall-effect and critical magnetic fields Hc2(T) have been studied for YNi2B2C (prepared using high pressure technique) at H≤130 kOe and 1.6≤T≤300K. The normal state Hall coefficient RH was found to be negative (RH=−1.43.10−11 Ωcm/Oe at T=4.2 K and H=130 kOe) and slightly growing in absolute value with increase of temperature. The dependence of the Hall voltage on magnetic field in the mixed superconducting state shows no sign reversal as was observed earlier for some high-Tc systems. The values of ¦∂Hc2/ ∂T¦and Hc2(0) are found to be 4.8 kOe/K and 47 kOe respectively.

The peculiarities of local structure of YbNi2 and YbCo2 intermetallics synthesized at high pressure.

Local structure of YbCo2 and YbNi2 was investigated by EXAFS and XANES spectroscopy. It was found that the bond Yb-Co(Ni) has the highest static disorder and its length increases with temperature decrease, while all other bonds remain almost unchanged. This phenomenon may be caused by short-range magnetic ordering at temperatures above the phase transition. XANES measurements above ZIII-Yb absorption edge in YbCo2 and YbNi2 revealed that both compounds have almost the same density of free 5d-states