Magnetism of YMn6Sn6 and DyMn6Ge6: Single-crystal Study
The magnetic properties of YMn6Sn6 and DyMn6Ge6, which crystallize in the hexagonal HfFe6Ge6-type of structure, have been studied on single crystals that have been prepared in an Sn flux and In flux, respectively. The compounds order antiferromagnetically at about 330 K and 450 K and exhibit very complex magnetic properties in the magnetically ordered state. The evolution of the magnetization in the ordered state has been investigated in the temperature region from 2 to 550 K and magnetic field up to 14 T.
Incommensurate magnetic structures of RMn6Sn6(R = Sc, Y, Lu) compounds from neutron diffraction study
Abstract Neutron diffraction measurements have been performed on the ternary compounds YMn 6 Sn 6 , LuMn 6 Sn 6 and ScMn 6 Sn 6 of HfFe 6 Ge 6 -type structure (space group, P6/mmm ). All three compounds order antiferromagnetically at 333 K, 353 K and 384 K for R = Y, Lu and Sc respectively. In the whole temperature range for YMn 6 Sn 6 and ScMn 6 Sn 6 and below room temperature for LuMn 6 Sn 6 , the magnetic structure is a flat spiral consisting of ferromagnetic (001) “MnSnSnMn” sheets (with the moments μ Mn ≈ 2.15 μ B at 2 K in the layers) stacked along the c axis in the sequence MnRMnSnSnMnRMn. In each case, according to the occurrence of several thermally dependent modulation vectors, the magnetic structure has been refined considering an inhomogeneous mixture of magnetic phases, each of them being characterized by a different wavevector. Under these conditions, the magnetic moments change their orientation by about 40°–60° within the basal plane on going from one R sheet to another. In the case of YMn 6 Sn 6 , a complex unique arrangement with a non-constant rotation of the moments has also been considered, i.e. a turn-angle sequence [1 × 160°−7 × 114.7°−2 × 27°−7 × 114.7°−1 × 160°] along one-half the c ′ parameter of a supercell with c ′ = 36 c . A discussion and some comparisons with the parent CoSn B35-type structure binary compounds, on the one hand, and the other RMn 6 Sn 6 compounds, on the other hand, are given in conclusion.
Magnetic structures of TbMn6Sn6 and HoMn6Sn6 compounds from neutron diffraction study
Abstract Neutron diffraction measurements have been performed on the ternary stannides TbMn6Sn6 and HoMn6Sn6 of HfFe6Ge6 type structure (space group, P6/mmm). This structure can be described as a filled derivative of the CoSn B35-type structure. Each of the rare earth and manganese atoms is successively distributed in alternate layers stacked along the c axis with the sequence Mn-R-Mn-Mn-R-Mn. Owing to the manganese atom coordination of the rare earth, this structure appears closely related to the CaCu6- and ThMn12-type structures. This study confirms that both the rare earth and the manganese sublattices order simultaneously above room temperature. In the whole temperature range studied (2–300 K), TbMn6Sn6 and HoMn6Sn6 exhibit a collinear ferrimagnetic arrangement. At 300 K, the magnetic structure consists of a stacking of ferromagnetic (001) layers of rare earth and manganese with the coupling sequence Mn(+)R(−)Mn(+)Mn(+)-R (−)Mn(+) (μMn ≈ 2.0(1)μB, μTb = 4.9(1)μB, μHo = 4.7(1)μB). For HoMn6Sn6, the magnetic moments lie in the (001) plane while in TbMn6Sn6, they deviate by φ = 15° from the c axis. Below 300 K, the two compounds exhibit a spin rotation process and at 2 K the magnetic moments are along [001] and at 50° from this axis for TbMn6Sn6 and HoMn6Sn6 respectively μMn = 2.4(1)μB, μTb = 8.6(1)μB, μHo = 8.4(1)μB). The results are discussed in terms of Ruderman-Kittel-Kasuy-Yoshida exchange interactions and compared with those obtained previously for the parent RFe6Al6 and RCo6 compounds.