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

TL;DR

This study used neutron diffraction to determine the magnetic structure of single-crystalline UAu₂Si₂, revealing an antiferromagnetic order with a specific propagation vector and a squared-up structure with ferromagnetic planes stacked along the a-axis.

Contribution

It provides the first detailed magnetic structure of UAu₂Si₂, combining neutron diffraction, group theory, and other experimental data to clarify its antiferromagnetic ordering.

Findings

Antiferromagnetic order below 20 K with propagation vector (2/3, 0, 0)

Magnetic moments aligned along the c-axis

Stacking sequence of ferromagnetic sheets is (+ + -)

Abstract

Magnetic structure of tetragonal UAu$_2$Si$_2$ was investigated by single-crystal neutron diffraction experiments. Below $T_{\rm N}$ = 20 K it orders antiferromagnetically with a propagation vector of $k = (2/3, 0, 0)$ 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$_2$.