Spin order and excitations in the collinear kagome antiferromagnet ${\rm Y_{0.5}Fe_3Sn_3}$
Kagome lattices host rich magnetic, topological, and transport phenomena owing to their geometric frustration and strong spin correlations. Here we present a systematic neutron scattering study of the kagome metal Y$_{0.5}$Fe$_3$Sn$_3$, which orders into a collinear $c$-axis antiferromagnetic (AF) state below $T_N =$ 5...