Investigation of Scaling Laws by Critical Neutron Scattering from Beta-Brass

Using a ${\mathrm{Cu}}^{65}$-Zn $\beta$-brass crystal, the critical scattering of neutrons has been studied, both above and below $T_c$. The staggered susceptibilities $\chi$ vary as $C_{+}{(\frac{T}{T_c}-1)}^{-\gamma }$ and $C_{-}{(1-\frac{T}{T_c})}^{-{\gamma }^{\prime }}$, respectively. We find that $\gamma ={\gamma }^{\prime }$ within an accuracy of 3%, in agreement with the scaling hypothesis of static critical phenomena; and that $\frac{C_{+}}{C_{-}}=5.46\mathrm{}\pm 0.05$, in excellent agreement with the recent parametric representation theory of Schofield and in fair agreement with the results of series expansions by Essam and Hunter. For fixed $q$, a flat maximum is observed in the wave-vector-dependent susceptibility $\chi (q, T)$ at temperatures which agree well with the predictions of Fisher and Burford.