Incommensurate-commensurate magnetic phase transition inSmRu2Al10

Abstract

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 Sm 3+ 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 the magnetic structure, we propose that the long-range RKKY interaction plays an important role, in addition to the strong nearest neighbor antiferromagnetic interaction.

Temperature-Dependent Cycloidal Magnetic Structure in GdRu2Al10Studied by Resonant X-ray Diffraction

“…Interestingly, the q value seems to start from nearly 0.75 just below T N1 = 17.5 K. Note that q ∼ 0.75 is a value commonly observed in other RT 2 Al 10 compounds such as NdFe 2 Al 10 and SmRu 2 Al 10 . 15,16) The similar result for GdRu 2 Al 10 seems to show that q ∼ 0.75 is the fundamental propagation vector of the RKKY interaction in the RT 2 Al 10 system. It is also noteworthy that the temperature dependence of the q value is very similar to that of the order parameter.…”

“…[12][13][14] In isostructural NdFe 2 Al 10 and SmRu 2 Al 10 , on the other hand, the magnetic structure is described by q = (0, 3/4, 0) and its third harmonic of (0, 1/4, 0), reflecting the squaring up. 15,16) The high-temperature phase of SmRu 2 Al 10 is an incommensurate phase with q = (0, 0.759, 0). There is also a case of q ≃ (0, 0.798, 0) as in TbRu 2 Al 10 .…”

Magnetic structure and crystal field excitations of NdOs2Al10: a neutron scattering study

“…There are no signs of magnetic Bragg peaks resulting from higher harmonics of the modulation indicating that the sine wave does not square up. This is different to the situation found in the corresponding Fe-compound NdFe 2 Al 10 [30] and in SmRu 2 Al 10 [20] which both see the presence of two magnetic propagation vectors where one can be described as the third harmonics of the other. A complete squaring up of the sine wave modulated structure had been found in the only other T = Ru/Os compound TbRu 2 Al 10 [19] where the magnetic structure is known.…”

“…Surprisingly, the very high research activity connected to the Ce-compounds did up to now not lead to an intensive study of the magnetic structures of other RT 2 Al 10 (R = Nd to Tm, T = Ru, Os) compounds. Information exists just for TbRu 2 Al 10, which sees a sine wave modulated structure along the b-axis with moments pointing in the c-direction [19], and for SmRu 2 Al 10 , which sees first a longitudinal spin wave structure and at lower temperatures a lock-in transition to a commensurate magnetic structure with moments pointing along the b-axis [20]. Both magnetic structures confirm the predominance of RKKY interactions in these compounds and point thereby again to the exceptional situation of the Ce-compounds.…”

Crystal symmetry lowering in chiral multiferroic Ba3TaFe3Si2O14 observed by x-ray magnetic scattering

“…In rare-earth metals that have a ĉ-axis spiral spin structure 28 , the third harmonic originates from higher order resonant processes. In contrast to the rare-earth metals 35 , presence of higher-rank multipoles is unlikely for 3d metals, and hence were neglected in Eqs. (3) and (4).…”