MAGNETIC-PROPERTIES OF THE CARBIDES RCOC (R=Y, GD-ER, LU) WITH YCOC-TYPE STRUCTURE

The magnetic properties of the carbides RCoC (R = Y, Gd-Er, Lu) were d etermined with a SQUID magnetometer between 2 and 300 K at magnetic fl ux densities of +/-5.5 T. The cobalt atoms of these carbides do not ca rry magnetic moments as is indicated by the Pauli paramagnetism of the yttrium and the lutetium compound. The others Show Curie-Weiss behavi our and the magnetic moments correspond to those of the free R(3+) ion s. The reciprocal susceptibility curves of GdCoC and TbCoC suggest fer romagnetism with Curie temperatures of T-c = 16(3)K and 22(2) K, respe ctively. While the terbium compound shows a narrow hysteresis loop at 5 K, no remanence and no coercitivity was found for the gadolinium com pound at this temperature. DyCoC, HoCoC and ErCoC are metamagnetic wit h Neel temperatures between 8 and 4 K. The new isotypic carbide YbCoC was prepared from a lithium flux. It has the tetragonal lattice consta nts a = 362.6(1) pm, c = 662.5(2) pm.