Weak ferromagnetism in

magnetic properties of (₁₋ₓₓ)₃ have been studied. The ac susceptibility \χ = \χ' + \χ'' been measured at frequencies ranging from 10 Hz to 1 000 Hz. The x = 0.25 shows a typical ferromagnetic behaviour with a dimensionless SI of 6 below T_ = 350 limited by the field. Both x = 0 and x = 0.06 crystals show very sharp in \χ' and \χ'' at the Néel points, 139 K and 135 K respectively. is quite unlike the usual behaviour of an antiferromagnet. measurements on an untwinned single crystal of ₃ a weak moment of 0.18 \μ_/ at 4.2 K which is along the c axis. The origin of this canted antiferromagnetic is discussed in terms of anisotropy and of Dzyaloshinskii-Moriya . It is concluded that anistropy is insufficient to explain canted antiferromagnetism.