Effects of Nd/Fe ratio on the microstructure and magnetic properties of NdFeB thin films

The effects of composition on the microstructure and magnetic properties of NdFeB thin films synthesized by DC magnetron sputtering from targets of Nd12.1Fe80.4B7.5 sintered magnet and Nd-chips have been investigated. The film with a compositional ratio of Nd/Fe = 17.6/82.4 deposited at the substrate temperature T-S = 700 degreesC showed soft magnetic properties with in-plane anisotropy. On increasing the compositional ratio to Nd/Fe = 27/73, the coercivity increased to about H-i(c) = 1500 kA/m (similar to 18.9 kOe), and a columnar structure was formed with a strong perpendicular magnetic anisotropy. Further increase of the ratio to Nd/Fe = 31/69 resulted in the increase of coercivity to about H-i(c) = 2070 kA/m (similar to 26kOe). The microstructure, however, changed to spherical grains and the perpendicular magnetic anisotropy decreased. The change of substrate temperature also affected the magnetic properties. The film with Nd/Fe = 27/73 deposited at a low temperature of T-S = 650 degreesC showed high remanence with low coercivity. The increase of the temperature of T-S = 700 degreesC resulted in high coercivity but low remanence. (C) 2001 Elsevier Science B.V. All rights reserved.