Types of Magnetic Order

In the case of rock salt, the cations form a face-centered-cubic (f.c.c.) array. Such an array is not compatible with a two-sublattice model, and there are four different types of magnetic order that can be considered (see Fig. 18). An f.c.c. structure is composed of four interpenetrating, simple-cubic (s.c.) sublattices. In ordering of the first kind, each s.c. sublattice is ferromagnetic and Mi = — M2, M3 = -M4 so that each cation has eight antiparallel and four parallel near neighbors. Then equation 101 becomes (all interactions assumed negative)... 

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