Neutron Diffraction Study on Single-crystalline UAu${}_2$Si${}_2$

Magnetic structure of tetragonal UAu${}_2$Si${}_2$ was investigated by single-crystal neutron diffraction experiments. Below $T_{\mathrm{N}}$ = 20 K it orders antiferromagnetically with a propagation vector of $k=(2\mathrm{/}3,0,0)$ and magnetic moments of uranium ions pointing along the tetragonal $c$-axis. Weak signs of the presence of a ferromagnetic component of magnetic moment were traced out.Taking into account a group theory calculation and experimental results of magnetization and ${}^{29}$Si-NMR, the magnetic structure is determined to be a squared-up antiferromagnetic structure, with a stacking sequence ($++-$) of the ferromagnetic $ac$-plane sheets along the $a$-axis. This result highlights similar magnetic correlations in UAu${}_2$Si${}_2$ and isostructural URu${}_2$Si${}_2$.