Fig. 4: Magnetic coupling constants as computed and shown along the (001) – or any of the equivalent (010) and (100) – crystallographic directions of the superlattice.
From: Persistent half-metallic ferromagnetism in a (111)-oriented manganite superlattice

The Mn are shown as circles, and the values of the coupling constants are reported in meV. Straight segments denote first nearest neighbours, whereas semicircles denote fourth-nearest neighbours, namely Mn two layers away but along the same Mn-O-Mn direction (whereas they vanish for all other Mn couples).