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Neutron Scattering from Magnetic Materials part 6

Tham khảo tài liệu 'neutron scattering from magnetic materials part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Representation analysis of magnetic structures 145 Table 9 Basis vectors of the rare earth atoms on the 14e Wyckoff position r 1g 0 r 2g 0 r 3g 0 0 0 0 r 4g S1x S2x S3x S4x S5x S6x 13 12 S5y S6y S1y S2y S3y S4y 23 22 S3z S4z S1z S2z S5z S6z 33 32 r 5g S3x S4x S5x S6x 0 13 11 S1y S2y S3y S4y 0 23 21 S1z S2z 5z S6z 0 33 31 r 1 u S1x S2x S3z S4z S5y S6y r 2u 0 r 3u S1x S2x s S5y S6y s S3 z S4z 12 21 s S1x S2x S5y S6y 2 S3 z S4z 22 1 1 r 4u S3y S4y S5z S6z 0 31 11 S3x S4x S1z S2z 0 23 21 S5x S6x S1y S2y 0 33 31 r 5u S3y S4y S5z S6z 0 13 V11 S3x S4x S1z S2z 0 23 21 S5x S6x S1y S2y 0 33 31 Fig. 3. Magnetic structure of Er6Mn23 viewed along 111 direction. The Er moments are symbolized by large arrows and the Mn moments by small arrows. 146 R. Ballou and B. Ouladdiaf 5.2. Second example k 0 5.2.1. Step 1 Crystal structure. The HoAuGe compound crystallizes in the hexagonal structure of the nonsymmorphic space group P63mc. The rare earth atoms occupy the 2a site 00z 00z 2 while Au and Ge occupy the 2b sites with different z values 32 z 3 1 z 2 . The compound orders antiferromagnetically below TN 5.6 K. 5.2.2. Step 2 Propagation vector. The powder diffraction patterns collected on the high flux diffractometer D1B at the Institut Laue-Langevin Grenoble France at 50 K and T 1.3 K are shown in Figure 4. The high temperature pattern is characteristic of the nuclear diffraction of the crystal structure. The neutron diagram can be refined in the hexagonal P63mc structure. The pattern at 1.3 K shows in addition to the high temperature peaks i.e. nuclear peaks new peaks due to an antiferromagnetic ordering. They can be indexed as hkl k with a propagation k 200 that is with respect to the chemical cell the magnetic cell is doubled in the a-direction below the Néel temperature TN 43 . 5.2.3. Step 3 Irreducible representations. We shall first of all determine the set a 0 a k k Kn for k 100 namely the little co-group G0 k from which the little group Gị is built up. The zeroth block a ra