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Magnetic structure of YMn6Ge6 and room temperature magnetic structure of LuMn6Sn6 obtained from neutron diffraction study

1993; Elsevier BV; Volume: 200; Issue: 1-2 Linguagem: Inglês

10.1016/0925-8388(93)90470-8

1873-4669

G. Venturini, R. Welter, B. Malaman, E. Ressouche,

Iron-based superconductors research

Neutron diffraction measurements have been performed on the ternary compounds YMn6Ge6 and LuMn6Sn6 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 (R) and Mn atoms are successively distributed in alternate layers, stacked along the c axis with the sequence MnRMnMnRMn. At 300 K, both compounds exhibit collinear antiferromagnetic arrangements and the magnetic structures consist of a stacking of ferromagnetic (001) layers of Mn with the coupling sequence Mn(+)RMn(−)Mn(−)RMn(+) (μMn ≈ 1.33(1)μB and 1.82(3)μB for LuMn6Sn6 and YMn6Ge6 respectively). For LuMn6Sn6, the magnetic moments lie in the (001) plane, while they are along the c axis in YMn6Ge6. At low temperature, a spin reorientation process occurs in both compounds, yielding incommensurate antiferromagnetic arrangements. For YMn6Ge6 (Tt ≈ 80 K), the Mn moments form a double-cone structure with a periodicity of about 105 Å (μMn = 1.95(4)μB at 2 K), while only preliminary results are available for LuMn6Sn6 below about 200 K. The results are compared with those obtained on the CoSnB35-type structure binary compounds FeSn and FeGe, on one hand, and the RMn6Sn6 compounds, on the other hand.