MnSc₂S₄ spinel with magnetic Mn²⁺ ions forming the diamond lattice is an
excellent model material for study magnetic frustration conceiving exotic states such as spiral spin liquid,  
competing long-range ordered phases and triple-q state in applied magnetic fields [1].
Neutron diffuse scattering gives direct experimental evidence for the existence of the spiral spin liquid
(T_N1=2.2 K <T< T_cw=23 K), which was predicted to occur in the J₁-J₂ model on the diamond lattice, when the ratio between the ferromagnetic first and antiferromagnegtic second neighbour couplings is |J₂/J₁|>0.125 [2].
Neutron single crystal diffraction unravels three long-range ordered phases supplanting each other on temperature lowering (T_N1=2.2 K, q₁=3/4 3/4 0; T_N2=1.75 K, q₂=3/4+d 3/4-d 0; T_N3=1.6 K, q₃=q₁) and, 
from the field variation of intensities of the different q₃ arms discloses the triple-q state.
With Monte Carlo simulations we scrutinize further details of the spin Hamiltonian, i.e. the third neighbour coupling, single ion anisotropy and exchange anisotropy and establish that this set of parameters
indeed stabilizes the lattice of dense topological objects akin to skyrmions [3].

1. S. Gao, O. Zaharko, V. Tsurkan, et al. Nature Physics, 13, 157 (2016).
2. D. Bergman, J. Alicea, E. Gull, S. Trebst, L. Balents,  Nature Physics 3, 487 (2007). 
3. S. Gao, D. Rosales, V. Tsurkan, O. Zaharko, et al. in preparation.