FIELD-DEPENDENCE OF MAGNETIC TRANSITIONS FOR MAGNETIC SUPERCONDUCTORSRNI(2)B(2)C (R=DY,HO)

High field (up to 5 T) magnetization measurements were performed on bo th bulk and field-aligned powder samples of RNi(2)B(2)C(R=Dy, Ho) magn etic superconductors. For T-c=3.8 K, a DyNi2B2C superconductor with an tiferromagnetic Neel temperature T-N Of 10-11 K, and anomalous field-i nduced weak-ferromagnetic transitions were observed above the supercon ducting upper critical field H-c2(2 K) of 1.75 kG. The aligned powders show distinct hysteresis characteristics for both fields applied para llel and perpendicular to the tetragonal basal plane. For T-c=7.8 K, H oNi2B2C has an incommensurate magnetic ordering temperature T-m of 5 K and T-N Of 5.2 K. Anomalous field-induced weak-ferromagnetic transiti ons were also observed below T-N. No hysteresis can be detected for T- N<T<T-m. (C) 1996 American Institute of Physics.