High-pressure effects in single crystals: RNi₂B₂C (R=Dy, Pr)

We report electrical resistivity studies for two magnetic borocarbides DyNi₂B₂C and PrNi₂B₂C single crystals under quasihydrostatic pressure, using a diamond anvil cell. The superconducting critical temperature for DyNi₂B₂C decreases in linear form with pressure at a rate dT_C/dP=-0.7 K/GPa up to about 1.8 GPa, above this pressure T_C decreases drastically. Measurements of resistivity versus pressure in DyNi₂B₂C show that the feature related with the antiferromagnetic order remain almost unchanged. At 5.3 GPa, PrNi₂B₂C does not show evidence of a superconducting transition. From the resistivity data due to spin disorder we have calculated the exchange-interaction strength between rare-earth ions as a function of pressure.