Neutron diffraction study of incommensurate magnetic order in TbOs2Si2 andHoOs2Si2

Neutron diffraction data collected at low temperatures for TbOs2Si2 and HoO s2Si2 indicate that in the former compound magnetic moments localized on Tb 3+ ions form an incommensurate, sine wave modulated structure with the wave vector k=(0.3138(5), 0, 0) and moments aligned along the tetragonal axis. This structure is stable between 1.5 K and the Neel point at 45 K. In HoOs2 Si2, an incommensurate magnetic order described by two wave vectors k(1)=(0 .3, 0, 0) and k(2)=(0.22, 0, 0) is observed between 1.5 and 8.6 K - the tra nsition temperature to a new also sine wave modulated magnetic phase with t he wave vector k=(0.3, 0, 0), stable up to the Neel point at 15.8 K. (C) 20 00 Elsevier Science S.A. All rights reserved.