Magnetic Interactions in Co₃O₄

Co 3 O 4 is a normal spinel with only A‐A interactions which becomes antiferromagnetic at T N ≈︁ 40 K. The exchange integrals between one ion and its first and second neighbours are derived from the second moment of energy distributions of neutrons scattered by a polycrystalline sample in its paramagnetic state (155 K) and from a Green's function analysis of T N . The result, J 1 /k B = −(7.27 ± 0.25) K and |J 2 |/k B < 0.3 K, indicates that the interaction with the nearest neighbours is by far dominant.