  Chiral helimagnetism was investigated in transition-metal intercalated
dichalcogenide single crystals of MnTa$_3$S$_6$. Small-angle neutron scattering
(SANS) experiments revealed the presence of harmonic chiral helimagnetic order,
which was successfully detected as a pair of satellite peaks in the SANS
pattern. The magnetization data are also supportive of the presence of chiral
soliton lattice (CSL) phase in MnTa$_3$S$_6$. The observed features are
summarized in the phase diagram of MnTa$_3$S$_6$, which is in strong contrast
with that observed in other dichalcogenides such as CrNb$_3$S$_6$ and
CrTa$_3$S$_6$. The presence of the remanent state provides tunable capability
of the number of chiral solitons at zero magnetic field in the CSL system,
which may be useful for memory device applications.
