Hall-effect in LuNi_2B_2C and YNi_2B_2C borocarbides: a comparative study

TL;DR

This study compares the Hall effect in LuNi_2B_2C and YNi_2B_2C borocarbides, revealing similar behaviors in superconducting states but notable differences in normal state properties linked to Fermi surface topology.

Contribution

It provides a comparative analysis of Hall effect behaviors in two borocarbide compounds, highlighting the influence of disorder, flux pinning, and Fermi surface differences.

Findings

Hall resistivity is negative in both compounds with no sign reversal below T_c.

Scaling relation rho_{xy} ~ rho_{xx}^beta with beta ~ 2 varies with disorder and annealing.

LuNi_2B_2C shows nonlinear rho_{xy}(H) and high magnetoresistance, unlike YNi_2B_2C.

Abstract

The Hall effect in LuNi_2B_2C and YNi_2B_2C borocarbides has been investigated in normal and superconducting mixed states. The Hall resistivity rho_{xy} for both compounds is negative in the normal as well as in the mixed state and has no sign reversal below T_c typical for high-T_c superconductors. In the mixed state the behavior of both systems is quite similar. The scaling relation rho_{xy}\sim\rho_{xx}^\beta (\rho_{xx} is the longitudinal resistivity) was found with \beta=2.0 and 2.1 for annealed Lu- and Y-based compounds, respectively. The scaling exponent \beta decreases with increasing degree of disorder and can be varied by annealing. This is attributed to a variation of the strength of flux pinning. In the normal state weakly temperature dependent Hall coefficients were observed for both compounds. A distinct nonlinearity in the \rho_{xy} dependence on field H was found for LuNi_2B_2C in the normal state below 40K, accompanied by a large magnetoresistance (MR) reaching +90% for H=160kOe at T=20K. At the same time for YNi_2B_2C only linear \rho_{xy}(H) dependences were observed in the normal state with an approximately three times lower MR value. This difference in the normal state behavior of the very similar Lu- and Y-based borocarbides seems to be connected with the difference in the topology of the Fermi surface of these compounds.