ANISOTROPIC ND-FE-B THIN-FILM MAGNETS FOR MILLI-SIZE MOTOR

Efforts were made to obtain anisotropic thin-film magnets at low substrate temperature. This is an important criterion for practical applications such as to build motors. The influence of substrate materials as well as film thickness on the c-axis orientation were studied. It has been shown that thin-film magnets with the easy axis of magnetization normal to the film plane could be deposited at a substrate temperature of around 450-degrees-C by choosing the composition near the line from Nd13Fe76B11 to Nd13Fe70B17 in the ternary phase diagram. It was found that the anisotropic film magnets could be also deposited on the metallic substrate. The c-axis orientation tended to be isotropic with an increase in film thickness. The obtained results were used to fabricate a milli-size motor by depositing 20-mu-m-thick Nd-Fe-B films on a silicon steel disk substrate of 5-mm diam. The milli-size motor exhibited a torque of 0.8 g mm at a rotational speed of 3000 rpm.