Single crystals of chromium-manganese alloys containing 0.12, 0.44 and 1.03 wt% Mn have been grown and their magnetic structures determined from 78 °K to their respective Néel temperatures. Measurements of the susceptibility of these crystals and of Young's modulus of the polycrystalline material have also been made over the same temperature ranges. The data confirm earlier magnetic structure work on polycrystalline material, and serve to illustrate a theory due to Tachiki and Nagamiya originally proposed to explain the antiferromagnetism of chromium.