An explanation is offered for the 30 degrees tipping of sublattices which h
as been observed in the noncollinear antiferromagnet CsMnI3. In contrast to
the ordinary 90 degrees spin flop, this phase transition is due to nonline
ar and relativistic corrections to the susceptibility. (C) 1998 American In
stitute of Physics. [S0021-3640(98)01223-7].