Magnetic powder, a hard magnetic single domain particle. It is made into magnetic slurry with adhesives, solvents, etc., and coated on the surface of plastic or metal substrate (support body) to make magnetic recording materials such as magnetic tapes, magnetic disks, and magnetic cards. Magnetic powder is the core component of magnetic coatings and the main factor determining the magnetic properties of magnetic recording media. Magnetic powder has a significant impact on the properties of magnetic recording materials. Therefore, there are certain requirements for magnetic particles: ① specific saturation magnetization σ S and coercivity Hc should be larger; ② The particles are finely needle shaped and uniform; ③ High dispersibility and filling ability in magnetic slurry; ④ Magnetically stable. It is difficult for magnetic powder to meet all the above requirements simultaneously. Commonly used magnetic particles include oxide magnetic particles and metal magnetic particles.