Abstract
Elastic neutron scattering is used to study the spin correlations in
the multiferroic antiferromagnet $\rm Mn_{1-x}Fe_{x}WO_4$ with
$x=0.035, 0.05$ and $0.10$. The noncollinear, incommensurate (ICM)
magnetic structure associated with the ferroelectric (FE) phase in
pure $\rm MnWO_4$ is suppressed at $x=0.035$ and completely absent
at $x=0.10$. The ICM spin order and FE phase can be restored by
applying a magnetic field along the spin easy-axis. The low-$T$
commensurate magnetic structure extends in both H/T with increasing
Fe concentration. The systematic evolution of the magnetic and
electric properties indicates that the noncollinear ICM spin order
results from competing magnetic interactions and its stabilization
can be tuned by the internal ($x$) or external (magnetic field)
perturbations.
