In this paper, we report an effective-medium theory on the remanence of magnetically interacting particles to demonstrate the effect of intergranular magnetostatic interactions on the remanence enhancement of materials, which agrees excellently with micromagnetic simulations. A dimensionless parameter λ measuring the competition between anisotropy energy and magnetostatic energy is defined, which completely characterizes the remanence of magnets if the exchange coupling is negligible, appropriate when the grain size is 10 nm or larger. Three distinct regimes were observed: $\lambda <0.1\mathrm{}$ for hard magnets, where anisotropy energy dominates and little remanence enhancement is observed; $0.1<\mathrm{}\lambda <1\mathrm{}$ for intermediate magnets where up to 50% remanence enhancement is observed due to the increased intergranular magnetostatic energy; and $\lambda >1\mathrm{}$ for soft magnets, where the dominance of magneto-static energy leads to much reduced remanence in the materials.

• Received 24 September 2003

DOI:https://doi.org/10.1103/PhysRevB.68.212402