Microstructure, magnetic properties, and loss performance of the Cu-substituted MnZn ferrites

Abstract

While the Cu substitution in NiCuZn ferrites is known to enhance densification and increase the initial permeability (μi), little is known about its effects in the MnZn based ferrites, which naturally possess a higher saturation magnetization (Ms) and μi. In this study, the effects of Cu substitution for Mn on the power MnZn ferrites (Mn0.71-xCuxZn0.22Fe2.07O4, x = 0.00–0.35) are investigated. With increasing Cu content, enhanced density, reduced porosity, and significant grain growth are observed. The cation distribution was determined using the Rietveld refinement, showing the strong tendency of Cu2+ ions to occupy the octahedral sites of the spinel lattice. The magnetization curves show reduced Ms with increasing Cu content. The magnetic anisotropy (|K|) was also determined from the magnetization curves using the law of approach to saturation and is seen to be increased by the increasing Cu content. The reduced Ms and increased |K| lead to the dramatic reduction of μi from 2503 (x = 0.00) to 151 (x = 0.35) at room temperature. Despite the reduced Ms at room temperature, the Curie temperature (TC) is seen to increase with increasing Cu content from x = 0.05 to x = 0.35, indicating the relocation of cations at an elevated temperature. The cut-off frequency (fr) is increased with increasing Cu content, which corresponds to the reduced μi. Moreover, the core loss (Pcv) of the MnCuZn ferrites was tested at 100kHz/200 mT, 200kHz/125 mT, and 300kHz/100 mT at room temperature, and is found to deteriorate with the increasing Cu content.