As a magnetic recording unit, the size of magnetic particles must meet the following requirements: the length of particles shall be less than the recording wavelength; The width of particles should be much smaller than the recording depth; There should be as many magnetic particles as possible in a unit of recorded volume. Nano Fe2O3 has good magnetism and hardness. Oxygen magnetic materials mainly include soft magnetic iron oxide（ α- Fe2O3) and magnetically recorded iron oxide（ γ- Fe2O3) 。 Because of its small size, single domain structure and high coercivity, magnetic nanoparticles can be used to make magnetic recording materials to improve the signal-to-noise ratio. At present, the magnetic ultrafine particles commonly used in video tapes are needle like particles of iron or iron oxide (such as needle like particles γ- Fe2O3)。 Of course, the prospect of magnetic recording materials is increasingly challenged by new materials such as semiconductor materials and carbon nanotubes. At present, the solid-state disk technology using semiconductor materials has been very mature, but it is undeniable that the traditional hard disk using ferromagnetic oxide recording materials is still the most cost-effective storage device.
