Studies on the magnetic properties for single-phase nanocrystalline FePt magnets with different orientation degrees

The single-phase nanocrystalline FePt magnets composed of 343 irregular-shaped grains are built. The demagnetization curves are simulated by micromagnetic finite element method. The remanence, coercivity and maximum energy product of the magnets decrease with deteriorating grain alignment. The characteristics of variation of magnetic properties with the degree of orientation are closely related to the average grain size of nanocrystalline magnets. The contribution of intergrain exchange coupling (IGEC) to remanence enhancement is associated to the degree of orientation, and decreases with improved grain alignment. With decreasing grain size, coercivity increases for anisotropic nanocrystalline magnets, which is completely different from that of isotropic nanocrystalline magnets.