Fig. 1: Candidate magnetic structures.

Basic candidate structures for Gd₂Ti₂O₇, showing a 1-k, b 2-k, c 3-k, and d 4-k structures. The symmetry of each structure is labeled. A single crystallographic unit cell is shown in each case; spin orientations are reversed in adjacent unit cells because of the \({{{\bf{k}}}}=(\frac{1}{2}\frac{1}{2}\frac{1}{2})\) propagation vector. Spin directions are shown as arrows with lengths proportional to the ordered moment magnitude μ_ord, and the spin planes of triangular plaquettes for the 1-k and 4-k structures are shaded gray. Arrows of different colors indicate symmetry-inequivalent magnetic sites, and paramagnetic sites with zero μ_ord in a, c, and d are shown as gray spheres.