Incommensurate-Commensurate Magnetic Phase Transition in SmRu$_{2}$Al$_{10}$

TL;DR

This study investigates the magnetic phase transitions in SmRu₂Al₁₀, revealing an incommensurate to commensurate transition at low temperatures through various experimental techniques and resonant x-ray diffraction.

Contribution

It provides detailed magnetic structure analysis of SmRu₂Al₁₀, highlighting the incommensurate-commensurate transition and the role of RKKY interaction in magnetic ordering.

Findings

Successive magnetic phase transitions at 12.3 K and 5.6 K.

Incommensurate magnetic structure with q₁=(0, 0.759, 0).

Lock-in transition to a commensurate structure with q₁=(0, 0.75, 0).

Abstract

Magnetic properties of single crystalline SmRu$_{2}$Al$_{10}$ have been investigated by electrical resistivity, magnetic susceptibility, and specific heat. We have confirmed the successive magnetic phase transitions at $T_{\text{N}}=12.3$ K and $T_{\text{M}}=5.6$ K. Resonant x-ray diffraction has also been performed to study the magnetic structures. Below $T_{\text{N}}$, the Sm$^{3+}$ moments order in an incommensurate structure with $q_1=(0, 0.759, 0)$. The magnetic moments are oriented along the orthorhombic $b$ axis, which coincides with the magnetization easy axis in the paramagnetic phase. A very weak third harmonic peak is also observed at $q_3=(0, 0.278, 0)$. The transition at $T_{\text{M}}$ is a lock-in transition to the commensurate structure described by $q_1=(0, 0.75, 0)$. A well developed third harmonic peak is observed at $q_3=(0, 0.25, 0)$. From the discussion of the magnetic structure, we propose that the long-range RKKY interaction plays an important role, in addition to the strong nearest neighbor antiferromagnetic interaction.