MAGNETIC-PROPERTIES OF SINGLE-CRYSTAL GDNI2B2C

Single crystals of GdNi2B2C have been grown out of Ni2B flux at high t emperatures. Temperature and field dependent magnetization measurement s on these crystals show that in low fields (1 kG) there are two phase transitions: at 20 K there is a paramagnetic to antiferromagnetic pha se transition and at 14 K there is another transition which we infer t o be a spin reorientation transition. The lower temperature transition manifests itself clearly in the anisotropic magnetization data, but i s effectively averaged out in measurements of a powdered sample as wel l as in the polycrystalline average of the anisotropic magnetization d ata. Both of these transitions are also conspicuous in the temperature dependent electrical resistivity. GdB2C2 single crystals were also gr own out of Ni2B flux. This compound has an antiferromagnetic phase tra nsition at 47 K and is very likely an impurity phase responsible for t he earlier, spurious, report of a 45 K phase transition in GdNi2B2C.