[en] The critical behaviour of the dilute antiferromagnetic substance (Crsub(x)Alsub(1-x))₂O₃ is measured by neutron diffraction and the critical exponent β of the magnetization of the sublattices is determined as a function of the concentration ratio. (Crsub(x)Alsub(1-x))₂O₃ is an Ising system with statistically distributed local magnetic moments. For growing dilution of the magnetic moments and close by the percolation limit a raise of the exponent β is observed. Thus the result supports the theory that the exponent β depends on the concentration. (BHO)