Abstract: The effects of grain size on the random anisotropy constant 〈Keff〉 in Nd2Fe14B/αFe nanocomposite magnet have been investigated. The results show that 〈Keff〉 of the magnet decreases with the increase of the size of soft magnetic grain (Ds) and the decrease of the size of hard one (Dh), and if the magnet wants to obtaind bigger random anisotropy, Ds should decrease to 10 nm or so and Dh should increase as far as possible, and if the magnet expects to have higher magnetic energy product, Dh should be bigger than 10 nm and Ds should be 10 nm or so.

Key words: nanograin, nanocomposite magnetic material, exchangecoupling interaction , effective random anisotropy