# Frustration and Correlations in Stacked Triangular Lattice Ising Antiferromagnets

I will discuss multilayer triangular lattice Ising antiferromagnets with interlayer interactions that are weak and frustrated in an {\it abc} stacking. We show that they exhibit a classical spin liquid regime at low temperature, in which both intralayer and interlayer correlations are strong but there is no long range order. Diffuse scattering in this regime is concentrated on a helix in reciprocal space, as observed for charge-ordering in the materials LuFe$_2$O$_4$ and YbFe$_2$O$_4$.

This talk is part of the Theory of Condensed Matter series.