Single-crystal and powder neutron diffraction experiments on<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">Fe</mml:mi><mml:mi mathvariant="normal">P</mml:mi><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>: Search for the magnetic structure

The long-accepted magnetic structure of $\mathrm{Fe}\mathrm{P}{\mathrm{S}}_{3}$ has recently been refuted through extensive powder neutron diffraction studies. Single-crystal neutron diffraction, using both quasi-Laue and monochromatic techniques, has now been conducted to reveal more information about the nature of the magnetic ordering in this compound. The magnetic unit cell was found to be twice as large as the crystallographic cell in both the $a$ and $b$ directions and around three times as large along the $c$ direction, giving a propagation vector of $[\frac{1}{2}\phantom{\rule{0.3em}{0ex}}\frac{1}{2}\phantom{\rule{0.3em}{0ex}}0.34]$. There is incomplete long-range magnetic order along the ${c}^{*}$ direction due to weak Fe-Fe interactions and large anisotropy in that direction. The variation of the spontaneous moment with temperature closely resembles that for an antiferromagnetic two-dimensional Ising model on a honeycomb lattice.