MAGNETIZATION MEASUREMENT OF THE CO MOMENT INDUCED BY THE MOLECULAR-FIELD IN Y1-TGDTCO3

The magnetization of polycrystalline Y1-tGdtCo3 with 0 less than or eq ual to t less than or equal to 1 has been measured up to 40 T, and the effect of the molecular field from the Gd sublattice on the itinerant metamagnetism of the Co sublattice is studied. The compounds with t < 0.25 show a field-induced metamagnetic transition of the Co sublattic e. A transition from the collinear magnetic structure to the non-colli near structure is observed in compounds with 0.50 less than or equal t o t less than or equal to 0.55. The spontaneous Co moment, which is ev aluated from the magnetization curve, exhibits a stepwise increase at t similar or equal to 0.25 when the Gd concentration is increased. Thi s means that the metamagnetic transition of the Co sublattice is induc ed by the molecular field from the Gd sublattice in Y1-tGdtCo3. The av erage intersublattice molecular-field coefficient lambda(GdCo) between the Gd and Co sublattices is estimated to be lambda(GdCo) = 40.9 +/- 0.4 T formula units/mu(B); the corresponding exchange coupling paramet er J(GdCo) is J(GdCo) = -(1.64 +/- 0.03) x 10(-22) J.