MAGNETIC-PROPERTIES OF SINGLE-CRYSTALLINE TBCOC2 AND TBNIC2 COMPOUNDS

Magnetic experiments have been performed on single-crystalline TbCoC2 and TbNiC2 compounds. The magnetic behaviors of TbCoC2 show that the magnetic structure below T(C) = 30 K is a simple collinear ferromagnetic one with the Tb moment of 8.45 mu(B) parallel to the a-axis. The various behaviors that appear in TbNiC2 with T(N) = 27.0 K are unexpected considering the collinear antiferromagnetic structure reported previously. The M-T curve shows a sharp cusp along both the b and the c-axes. Two field-induced transitions are observed in the M-H curve along the c-axis below 12 K. Four transitions appear as the temperature approaches T(N), and two of them continue to appear above T(N). The field-induced transition is also observed in the M-H curve along the b-axis. The results are interpreted satisfactorily by postulating a noncollinear antiferromagnetic structure, where the Tb moment of 7.34mu(B) cants its direction from the c-axis toward the b-axis by an angle of 11-degrees. A small spontaneous magnetization along the c-axis is explained by assuming a mismatched plane at a distance of 15.5b.