The R(6)Mn(23) (R = rare earth) compounds crystallize in the cubic Th6
Mn23-type structure with space group Fm ($) over bar 3m. Powder neutro
n-diffraction experiments were performed on Dy6Mn23 and Er6Mn23. The m
agnetic unit cell coincides with the chemical one. The R moments have
a ferromagnetic non-collinear arrangement, whereas the Mn moments are
parallel to the [111] direction. The magnetic structures belong to the
three-dimensional Gamma(5g) irreducible representation of Fm ($) over
bar 3m associated with the wave vector K = [000]. The spin configurat
ions in both compounds result from the competition between the R-R, R-
Mn magnetic interactions and the crystal electric field on the R ions.