When the spins of Ni-ferrite precipitates in a single crystal of Fe-doped NiO are coupled with the spins of the antiferromagnetic NiO matrix by exchange interaction across the interface, an exchange anisotropy is produced in each Ni-ferrite precipitate. FMR and magnetization measurements were performed together with electron micrographical examinations on the Ni-ferrite precipitates. The exchange anisotropy energy related to the coupling of spins between Ni-ferrite and NiO across the (111) interface was determined to be 0.9±0.1 erg/cm2. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.