  Two-dimensional (2D) layered materials, whether in bulk form or reduced to
just a single layer, have potential applications in spintronics and capacity
for advanced quantum phenomena. A prerequisite for harnessing these
opportunities lies in gaining a comprehensive understanding of the spin
behavior in 2D materials. The low dimensionality motivates an understanding of
the spin correlations over a wide length scale, from local to long range order.
In this context, we focus on the magnetism in bulk \MPSe ~and \MPS, 2D layered
van der Waals antiferromagnetic semiconductors. These materials have similar
honeycomb Mn layers and magnetic ordering temperatures, but distinct spin
orientations and exchange interactions. We utilize neutron scattering to gain
deeper insights into the local magnetic structures and spin correlations in the
paramagnetic and ordered phases by systematically investigating a
MnPS$_{x}$Se$_{3-x}$ ($x$ = 0, 1, 1.5, 2, 3) series of powder samples using
total neutron scattering measurements. By employing magnetic pair distribution
function (mPDF) analysis, we unraveled the short-range magnetic correlations in
these materials and explored how the non-magnetic anion S/Se mixing impacts the
magnetic correlations. The results reveal that the magnetism can be gradually
tuned through alteration of the non-magnetic S/Se content, which tunes the
atomic structure. The change in magnetic structure is also accompanied by a
control of the magnetic correlation length within the 2D honeycomb layers.
Complimentary inelastic neutron scattering measurements allowed a
quantification of the change in the magnetic exchange interactions for the
series and further highlighted the gradual evolution of spin interactions in
the series MnPS$_{x}$Se$_{3-x}$.
