MAGNETIC-SUSCEPTIBILITY OF RCO3B2 (R=Y, SM, GD, AND DY)

The temperature dependence of magnetic susceptibility has been measured in a temperature region from about 100 to 500 K for the compounds RCo3B2 With R=Y, Sm, Gd, and Dy. Their magnetization curves at T=5 K have also been measured in a pulsed high field up to 170 kOe. YCo3B2 seems to have a Pauli paramagnetic nature down to T=5 K. In the paramagnetic temperature region, SmCo3B2 exhibits Van Vleck paramagnetism; however, GdCo3B2 and DYCo3B2 show Curie-Weiss character. The paramagnetic susceptibility for all compounds mentioned above is found to include a Pauli paramagnetic contribution from the Co sublattice. In the case of GdCo3B2 at T=5 K, the magnetic moment of 0.2mu(B)/Co, which is antiparallel to the Gd moment, is considered to be induced by the exchange field from the Gd spin. A similar induced moment of 0.14mu(B)/Co is also estimated in DyCo3B2. The Sm- and Dy-sublattice moments at T=5 K are smaller than the free-ion values, which can be explained by the crystal-field theory. A relatively large value of B-2(0)=7.0 K for Dy3+ in DYCo3B2 can explain the experimental Dy3+ spontaneous moment and its increase by external field. The Sm moment in SmCo3B2 at T=5 K may be antiparallel to the induced Co-sublattice moment.