Long-range order inβ-brass studied by neutron diffraction

The long-range order, $M\left(T\right)\mathrm{}$, in $\beta$-brass has been measured by neutron diffraction from a small extinction-free crystal. The results agree with those obtained recently by x-ray diffraction. Near $T_c$ our data are in accordance with a power law $M\left(T\right)=D{(1-\frac{T}{T_c})}^{\beta }$ with the critical exponent $\beta =0.293\mathrm{}$ as predicted by the nearest-neighbor (nn) Ising model. However, our data give an amplitude $D=1.64\mathrm{}$ which is 10% higher than the nn Ising-model value.