Reorientation of antiferromagnetism in cobalt doped FeSn

FeSn is an itinerant antiferromagnet that hosts electronic Dirac states and ordered magnetic moments lying within its Fe Kagome-lattice planes. We present magnetization measurements of single crystals of $({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Co}}_{x})\text{Sn}$, revealing the evolution and suppression of this magnetic order with Co substitution. We interpret the dramatic changes in magnetic anisotropy to indicate a reorientation of the moments from perpendicular to parallel to the hexagonal $c$ axis and confirm this with neutron diffraction. It has been proposed that the Dirac nodes observed in FeSn should become gapped if the moments rotate as our data suggests. We identify Co-substituted compositions that adopt both antiferromagnetic configurations at different temperatures. This system provides a unique opportunity to study how the details of magnetic order impact Dirac electron states.