NEUTRON-DIFFRACTION STUDIES OF HO1-XYXNI2B2C COMPOUNDS

Neutron diffraction measurements have been carried out to investigate the nature of magnetic ordering in Ho1-xYxNi2B2C (x = 0, 0.1 and 0.2) compounds. HoNi2B2C shows a complex type of magnetic ordering below th e superconducting transition, with a commensurate antiferromagnetic or dering of the Ho moments below 5 K and a modulation of the magnetic or dering along a- and/or c-direction between 5 K < T < 8.5 K. The substi tution of Y for Ho alters the commensurate nature of the Ho ordering. In Ho0.9Y0.1Ni2B2C, satellite peaks corresponding to c-modulation appe ar below T-N and exist down to 2 K, together with the principal Bragg peaks. However, when the Y concentration is increased to 20%, the prin cipal Bragg peaks disappear and only the c-modulated satellite magneti c peaks are observed below T-N.