Hidden order in spin-liquid Gd3Ga5O12

Elucidating order within disorder In some materials, the geometry of the crystal lattice gets in the way of magnetic ordering. Their spins, although magnetically interacting, remain seemingly disordered and form a so-called spin liquid. Paddison et al. propose a different model for the spin-liquid compound Gd3Ga5O12. Neutron diffraction measurements and numerical techniques revealed that even though individual spins in this material were disordered, they formed 10-spin loops that were correlated with one another. The nature of this “hidden order” was such that it escaped direct detection by conventional techniques Science, this issue p. 179 Reverse Monte Carlo refinements of neutron diffraction data are used to deduce a model of ordered 10-spin loops in Gd3Ga5O12. Frustrated magnetic materials are promising candidates for new states of matter because lattice geometry suppresses conventional magnetic dipole order, potentially allowing “hidden” order to emerge in its place. A model of a hidden-order state at the atomic scale is difficult to deduce because microscopic probes are not directly sensitive to hidden order. Here, we develop such a model of the spin-liquid state in the canonical frustrated magnet gadolinium gallium garnet (Gd3Ga5O12). We show that this state exhibits a long-range hidden order in which multipoles are formed from 10-spin loops. The order is a consequence of the interplay between antiferromagnetic spin correlations and local magnetic anisotropy, which allows it to be indirectly observed in neutron-scattering experiments.