THE 2-COMPONENT NONCOLLINEAR ANTIFERROMAGNETIC STRUCTURES OF DYNIC2 AND HONIC2

DyNiC2 and HoNiC2, which crystallize in the orthorhombic space group A mm2, have been studied by neutron powder diffraction in the temperatur e range from 300 to 1.9 K. Both compounds exhibit modulated antiferrom agnetic configurations of the rare earth magnetic moments. The magneti c transition temperatures are 10 and 4 K for DyNiC2 and HoNiC2, respec tively. The magnetic structures are described by two propagation vecto rs: the commensurate k1 = [0, 0, 1] and the incommensurate k2 = [1/2 - tau, 1/3 + tau, k(z)] with tau = 0.03 and 0 and k(z) = 0.935 and 0.86 for DyNiC2 and HoNiC2 respectively. The magnitude and direction of th e magnetic moments are determined. The resultant non-collinear antifer romagnetic spin configurations are discussed with respect to crystal f ield and magnetic exchange interactions.