COMMENSURATE AND INCOMMENSURATE MAGNETIC-STRUCTURE COMPONENTS OF TB-(CO,NI)-DICARBIDES

Neutron powder diffraction has been performed on polycrystalline sampl es of TbCo1-xNixC2 with x = 0.15, 0.30, 0.50, 0.70, 0.85. Low-temperat ure diffraction patterns collected between 1.6 and 2.3 K are character ized by a variety of commensurate and incommensurate magnetic reflecti ons being attributed to different shares of ferromagnetic and antiferr omagnetic moment configurations in the different samples. When reducin g the Co concentration in favour of Ni, the magnetic order, which is c onfined to the Tb ions only, shows a crossover from ferro- to antiferr omagnetism accompanied by the formation of modulated moment components .