Incommensurate-commensurate magnetic phase transition in SmRu2Al10

Magnetic properties of single crystalline SmRu2Al10 have been investigated by electrical resistivity, magnetic susceptibility, and specific heat.We have confirmed the successive magnetic phase transitions at TN = 12.3 K and TM = 5.6 K. Resonant x-ray diffraction has also been performed to study the magnetic structures. Below TN, the Sm3+ moments order in an incommensurate structure with q1 = (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 q3 = (0,0.278,0). The transition at TM is a lock-in transition to the commensurate structure described by q1 = (0,0.75,0). A well-developed third harmonic peak is observed at q3 = (0,0.25,0). From the discussion of themagnetic structure,we propose that the long-range RKKY interaction plays an important role, in addition to the strong nearest-neighbor antiferromagnetic interaction.This work was supported by Grants-in-Aid for Scientific Research (Grants No. 24540376, No. 24340087, No. 15K05173, and No. 15K05175) from the Japan Society for the Promotion of Science (JSPS)