Anisotropic bonded magnet and preparation method thereof

An anisotropic bonded magnet, comprising an R-T-B permanent magnetic powder and an SmFeN permanent magnetic powder, wherein

• in the R-T-B permanent magnetic powder, the content of R is 28-31 wt. %, the content of B is 0.9-1.1 wt. %, and the balance is T;
• R is selected from one and more rare earth elements, T comprises Fe or FeCo and a small amount of transitional metal, and B is boron;
• the content of the SmFeN permanent magnetic powder is 5%-30% of the weight content of the R-T-B permanent magnetic powder;
• and
• the anisotropic bonded magnet is formed by pressing a plurality of different preforms, wherein the plurality of different preforms comprises preforms which are different in density and/or content of SmFeN permanent magnetic powder, and the plurality of different preforms comprises a first preform and a second preform, wherein a mass percentage content of SmFeN in the composite magnetic powder of the first preform is 5-13%, and a mass percentage content of SmFeN in the composite magnetic powder of the second preform is 15-30%;
• and a ratio of the density of the first preform and the second preform is 1:1.1 to 1:1.5;
• and in the magnet, the densities and/or SmFeN contents of the preforms arranged from the middle to two ends gradually decrease;
• or the densities and/or SmFeN contents of the preforms arranged from the center to the periphery gradually decrease;
• and
• the resulting anisotropic bonded magnet has a density deviation of less than 2% in a pressing direction;
• wherein the bonded magnet is a bonded magnetic ring having an aspect ratio of 2 to 8.