Scaling properties of the critical behaviour of the dilute antiferromagnet Fe_0.93Zn_0.07F₂

Critical scattering analyses for dilute antiferromagnets are made difficult by the lack of predicted theoretical line shapes beyond mean-field models. Nevertheless, with the use of some general scaling assumptions we have developed a procedure by means of which we can analyse the equilibrium critical scattering in these systems for H = 0, the random-exchange Ising model, and, more importantly, for H > 0, the random-field Ising model. Our new fitting approach, unlike the more conventional techniques, allows us to obtain the universal critical behaviour exponents and amplitude ratios as well as the critical line shapes. We discuss the technique as applied to Fe_0.93Zn_0.07F₂. The general technique, however, should be applicable to other problems where the scattering line shapes are not well understood but scaling is expected to hold.