Magnetic structure of Sm₂IrIn₈ determined by x-ray resonant magnetic scattering

The magnetic structure of the intermetallic antiferromagnet Sm₂IrIn₈ was determined using x-ray resonant magnetic scattering. Below T_N=14.2 K, Sm₂IrIn₈ has a commensurate antiferromagnetic structure with a propagation vector η⃗=(1∕2,0,0). The Sm magnetic moments lie in the ab plane and are rotated roughly 18° 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 L₂ edge. At the L₃ edge, both quadrupolar and dipolar features were observed in the energy line shape. The magnetic structure and properties of Sm₂IrIn₈ are found to be consistent with the general trend already seen for the Nd-, Tb-, and the Ce-based compounds from the R_mM_nIn_3m+2n family (R=rare earth; M=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 Néel temperature for Sm₂IrIn₈ is slightly suppressed when compared to the T_N of the parent cubic compound SmIn₃.