Fig. 6.

Schematic view of magnetic planes of SCBO in the unit cell. A and B show the schematic views of the projections of the spin orientations of Cu²⁺ ions of SCBO along the (A) a–b and (B) a–c crystallographic planes according to the 2D antiferromagnetically ordered Shastry–Sutherland model. (C and D) Schematic views of the projections of the spin orientations of Cu²⁺ ions of SCBO along the (C) a–b and (D) a–c crystallographic planes according to the modified model described in the text. The effects of the anisotropic DM interaction in the 3D long-range ordered phase results in the slight divergence of the projections of the spin orientations from exactly parallel–perpendicular to the dimer axes alignments. B and D show that in the proposed 3D compared with the pure Shastry–Sutherland 2D ordering, the dimers are tilted with respect to the a–b plane and their bonds are expanded (red) and contracted (blue).