ITINERANT METAMAGNETISM OF THE CO-SUBLATTICE IN THE Y1-XNDXCO3 SYSTEMIN ULTRAHIGH MAGNETIC-FIELDS UP TO 110-T

Magnetization measurements have been carried out for Y1-xNdxCo3 compou nds with 0 less-than-or-equal-to x less-than-or-equal-to 1 in ultrahig h magnetic fields up to 110 T. The compound exhibits two metamagnetic transitions of the Co sublattice to a higher moment state. Both transi tion fields decrease with increasing Nd concentration due to the excha nge field from the Nd sublattice acting on the Co sublattice. From the concentration dependence of the transition fields the average exchang e parameter between Nd and Co is estimated to be J(NdCo) = 2.0 x 10(-2 2) J. The spontaneous Co moment and the Curie temperature also exhibit an anomalous increase with Nd concentration, which originates from th e transitions.