  It has been proposed that a line junction between spiral magnet and
superconductor or between ferromagnet and superconductor with Rashba
spin-orbital coupling can produce Majorana zero mode (MZM) at the ends of the
line. However, a strong magnetic exchange coupling between the magnetic atoms
and the superconductor (about half of the bandwidth of the superconductor) is
needed to obtain MZM. Here, we design devices to reduce the needed magnetic
exchange coupling. In the first proposal, we cover a very narrow $s$-wave
superconducting wire formed by a monolayer film or a layered material (such as
FeSe or FeSe monolayer on SrTiO$_3$) with \emph{isolated} magnetic atoms. In
our second proposal, we place a line of \emph{isolated} magnetic \emph{ions} on
a monolayer superconductor or a \emph{layered} superconductor (such as FeSe).
We show that, in the above devices, a spiral magnetic order will develop
spontaneously to produce a 1D $p$-wave topological superconductor with a
sizable gap (above 1/2 of the parent superconducting gap), even for a weak
magnetic exchange coupling (less than 1/10 of the bandwidth). The topological
superconductor has MZM at ends of the wire.
