Detailed study of the magnetic phase transitions in single crystalline HoNi2B2C and DyNi2B2C

Abstract We have studied the magnetic phase transitions in single phase, single crystalline HoNi 2 B 2 C and DyNi 2 B 2 C by measuring the temperature-dependent magnetic susceptibility, specific heat, and electrical resistivity. This study was undertaken in order to clarify the question of whether DyNi 2 B 2 C has a second, higher temperature magnetic phase transition near 16 K. HoNi 2 B 2 C has a cascade of magnetic phase transitions between 5 and 6 K. In addition to the superconducting phase transition near 9 K, three magnetic transitions (6.0, 5.5, and 5.2 K) can be easily detected in both of the thermodynamic measurements and are also seen in the electrical transport. The data taken on HoNi 2 B 2 C clearly demonstrates that multiple magnetic phase transitions can be readily detected (when they are actually present). In the case of DyNi 2 B 2 C only one magnetic phase transition (at T N ∼10 K ) was detected. The only other phase transition associated with the DyNi 2 B 2 C sample was the lower temperature superconducting phase transition at 6.3 K. Despite extensive data collection and analysis, no sign of any phase transition between 10 and 20 K in DyNi 2 B 2 C could be detected. This leads us to the conclusion that there is no 16 K magnetic phase transition associated with single phase, single crystal DyNi 2 B 2 C.