Impurity Effects in Highly Frustrated Diamond Lattice Antiferromagnets

In this project, we study the effect of impurities in frustrated magnets with a highly degenerate ground state. We specialize to diamond lattice antiferromagnets with J₁-J₂ interactions. There, the ground state degeneracy is that of a surface, for couplings where J₂/J₁>1/8. More precisely, the spins order in a spiral whose wave-vector lies on any point of the "degeneracy surface" that corresponds to a given value of J₂/J₁.

We show that dilute impurities break the (ground state) degeneracy by selecting a "compromise" wave-vector in the degeneracy surface. The ground state in the presence of dilute impurities is the associated "compromise" spiral, locally deformed around impurities, making the system look like a "swiss cheese".