  The magnetic structure of the "nonmetallic metal" FeCrAs, a compound with the
characters of both metals and insulators, was examined as a function of
temperature using single-crystal neutron diffraction. The magnetic propagation
vector was found to be $\mathit{k}$ = (1/3, 1/3, 0), and the magnetic
reflections disppeared above $\mathit{T_{N}}$ = 116(1) K. In the ground state,
the Cr sublattice shows an in-plane spiral antiferromagnetic order. The moment
sizes of the Cr ions were found to be small, due to strong magnetic frustration
in the distorted Kagome lattice or the itinerant nature of the Cr magnetism,
and vary between 0.8 and 1.4 $\mu_{B}$ on different sites as expected for a
spin-density-wave (SDW) type order. The upper limit of the moment on the Fe
sublattice is estimated to be less than 0.1 $\mu_{B}$. With increasing
temperature up to 95 K, the Cr moments cant out of the $\mathit{ab}$ plane
gradually, with the in-plane components being suppressed and the out-of-plane
components increasing in contrast. This spin-reorientation of Cr moments can
explain the dip in the $\mathit{c}$-direction magnetic susceptibility and the
kink in the magnetic order parameter at $\mathit{T_{O}}$ ~ 100 K, a second
magnetic transition which was unexplained before. We have also discussed the
similarity between FeCrAs and the model itinerant magnet Cr, which exhibits
spin-flip transitions and SDW-type antiferromagnetism.
