Magnetic structure of Sm_ {2} IrIn_ {8} determined by x-ray resonant magnetic scattering

The magnetic structure of the intermetallic antiferromagnet ${\mathrm{Sm}}_{2}\mathrm{Ir}{\mathrm{In}}_{8}$ was determined using x-ray resonant magnetic scattering. Below ${T}_{N}=14.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, ${\mathrm{Sm}}_{2}\mathrm{Ir}{\mathrm{In}}_{8}$ has a commensurate antiferromagnetic structure with a propagation vector $\stackrel{P\vec}{\ensuremath{\eta}}=(1∕2,0,0)$. The Sm magnetic moments lie in the $ab$ plane and are rotated roughly 18\ifmmode^\circ\else\textdegree\fi{} away from the $a$ axis. The magnetic structure of this compound was obtained by measuring the strong dipolar resonant peak whose enhancement was of over 2 orders of magnitude at the ${L}_{2}$ edge. At the ${L}_{3}$ edge, both quadrupolar and dipolar features were observed in the energy line shape. The magnetic structure and properties of ${\mathrm{Sm}}_{2}\mathrm{Ir}{\mathrm{In}}_{8}$ are found to be consistent with the general trend already seen for the Nd-, Tb-, and the Ce-based compounds from the ${R}_{m}{M}_{n}{\mathrm{In}}_{3m+2n}$ family ($R=\text{rare}$ earth; $M=\mathrm{Rh}$ or Ir; $m=1,2$; $n=0,1$), where the crystalline electrical field effects determine the direction of magnetic moments and the ${T}_{N}$ evolution in the series. The measured N\'eel temperature for ${\mathrm{Sm}}_{2}\mathrm{Ir}{\mathrm{In}}_{8}$ is slightly suppressed when compared to the ${T}_{N}$ of the parent cubic compound $\mathrm{Sm}{\mathrm{In}}_{3}$.