Magnetic Structure of ErAu2

The magnetic properties of ErAu₂ having the tetragonal body‐centered CaC₂‐type structure have been investigated at temperatures between 297 and 1.8°K by neutron diffraction experiments on powdered specimens. The onset of an incommensurate, transverse wave moment alignment (the α structure) occurs at 6.7°K. The α magnetization wave propagates along the a axis and is polarized in the b direction, all in the face‐centered description. The α wavelength is 6.443 Å = 1.248 a and is temperature independent. At 4.0°K, a commensurate antiferromagnetic moment wave (the β structure) appears with the propagation direction parallel to the a axis. The β wavelength is equal to the a spacing. As regards the β moment components, the $\mathrm{x\; \parallel \; a}$ component is slightly larger than the $\mathrm{y\; \parallel \; b}$ component and the $\mathrm{z\; \parallel \; c}$ component is undetectably small. The composite configuration of the α and β waves delineates a distorted‐fan modulation. In cooling, the α amplitude develops to 6.7 μ_B at 4°K, then decreases to 5.9 μ_B near 3°K, and retains 5.9 μ_B at $\text{3>T>0°}\mathrm{K}$ . The β wave moments approximate the Brillouin magnetization with the extrapolated moments of 3.2 and 2.7 μ_B at 0°K for the x and y components, respectively. The maximum composite moment is 9.2 μ_B at 0°K, while the ordered moment of the free Er³⁺ ion is 9.0 μ_B.