Neodymium-iron-boron permanent magnet and preparation method thereof

The invention provides a neodymium iron boron permanent magnet and a preparation method thereof. The preparation method of the neodymium-iron-boron permanent magnet comprises the following steps: preparing powder from copper powder, aluminum powder, lanthanum powder, boron powder, neodymium powder and iron powder; the powder is sequentially subjected to vacuum melting, melt-spinning flaking, hydrogen demolishing treatment and airflow grinding, and matrix magnetic powder is obtained; preparing composite magnetic powder from ammonium bicarbonate, silicon nitride, zirconium powder, silicon powder and matrix magnetic powder; filling the matrix magnetic powder into a mold, and carrying out compression molding to obtain a blank body; mixing the composite magnetic powder with ethanol to prepare slurry, coating the surface of the blank with the slurry, and drying to obtain a green magnet; sintering the green magnet to obtain a sintered body; applying a heavy rare earth doping agent to the surface layer of the sintere