MAGNETIC-ORDERING IN RCOSN (R=DY, HO, ER) COMPOUNDS

Magnetic and crystal structures of DyCoSn, HoCoSn and ErCoSn were dete rmined by neutron diffraction on polycrystalline samples. All crystall ize in the orthorhombic, TiNiSi type of structure and order antiferrom agnetically below the following Neel points: 10 K (DyCoSn), 7.8 K (HoC oSn) and 5 K (ErCoSn). Magnetization against magnetic field strength c urves indicate a magnetic phase transition occuring at H = 0.26 and 0. 35 T in DyCoSn and HoCoSn, respectively. The magnetic structures of al l three compounds are square modulated with the wavevector k = [0, k(y ), 0], where k(y) is 5/7, 2/3 and 7/11 in DyCoSn, HoCoSn and ErCoSn, r espectively. The noncollinear ordering can be described by the A and G modes in terms of the Bertaut method.