Theoretical single-domain size of NiZn ferrite

The critical radius, R-c, below which a spherical particle of NiZn ferrite becomes a single domain in zero applied field. is computed by minimizing the energy under the only constraint that the magnetization configurations have a cylindrical symmetry. The rigorous result for an isolated particle is R-c = 22.3 nm. Several theories are used to correct for the soft environment of closely-packed particles, thus increasing R-c up to 0.727 mu m This value, however. is still too small to account for the experimental value of 1.4 +/- 0.05 mu m in NiZn ferrite. which means that bile problem of the effect of the soft environment needs a more careful theoretical study.