Ferromagnetic exchange coupling in the spinel lattice

The ferromagnetism of the recently discovered ferromagnetic spinels thought to be due to nearest neighbour Cr3+ superexchange interactions. The presence of such interactions is confirmed by measurements of the fluorescence of Cr3+ in the spinel ZnAl2O4. Structure is observed that may be clearly associated with exchange coupled Cr3+ pairs with a ferromagnetic exchange constant J = + 10.2 cm-1. © 1966.