Abstract
High field (up to 5 T) magnetization measurements were performed on both bulk and field-aligned powder samples of RNi <sub>2</sub> B <sub>2</sub> C (R=Dy, Ho) magnetic superconductors. For T <sub>c</sub> =3.8 K, a DyNi <sub>2</sub> B <sub>2</sub> C superconductor with antiferromagnetic Néel temperature T <sub>N</sub> of 10-11 K, and anomalous field-induced weak-ferromagnetic transitions were observed above the superconducting upper critical field H <sub>c2</sub> (2 K) of 1.75 kG. The aligned powders show distinct hysteresis characteristics for both fields applied parallel and perpendicular to the tetragonal basal plane. For T <sub>c</sub> =7.8 K, HoNi <sub>2</sub> B <sub>2</sub> C has an incommensurate magnetic ordering temperature T <sub>m</sub> of 6 K and T <sub>N</sub> of 5.2 K. Anomalous field-induced weak-ferromagnetic transitions were also observed below T <sub>N</sub> . No hysteresis can be detected for T <sub>N</sub> <T<T <sub>m</sub> . © 1996 American Institute of Physics.