Concurrent Core Loss Suppression and High Permeability by Introduction of Highly Insulating Intergranular Magnetic Inclusions to MnZn Ferrite

A novel approach entailing the introduction of incongruent insulating magnetic inclusions to the grain boundary region of polycrystalline ferrite cores has been proposed to target the eddy current loss as the major source of core loss at high operating frequency. To demonstrate the efficacy of this approach, highly resistive ferrimagnetic nanoparticles (NPs) of yttrium iron garnet (YIG) were introduced to the grain boundaries of MnZn ferrite. Diamagnetic NPs of barium titanate (BTO) were similarly added as a nonmagnetic insulating grain boundary control additive. A profound decrease was observed in the eddy current loss (up to 79%) by using this approach. For the case of magnetic inclusions, a retained high permeability (24% reduction) was achieved, whereas the samples with nonmagnetic additives experienced a considerable sacrifice to permeability (64% reduction). The sustained high permeability was attributed to the ferrimagnetic YIG NPs maintaining long-range magnetic interactions, whereas the BTO NPs both frustrated the eddy current and long-range intergranular magnetic interactions. These results indicate that low permeability is no longer a necessary constraint for suppression of core power loss.