Abstract: Exchange-coupling effect in anisotropy constant of nano-meter magnetic materials is investigated.An equation was put forward for anisotropy at grain boundaries.Due to exchange-coupling between magnetically soft and hard grains,anisotropy of hard grain is decreased while that of soft grain is enhanced.The average anisotropy of soft-hard grains,increases rapidly,reaches a maximum and then decreases slowly.It is consistent with related experimental and theoretic results.Calculated average anisotropy of hard grains is consistent with experiment.

Key words: nanomaterials, random anisotropy model, exchange-coupling interaction