Barium hexaferrites with narrow ferrimagnetic resonance linewidth tailored by site‐controlled Cu doping

Abstract

Barium hexagonal ferrites exhibiting unique self-biasing characteristics have great potential for application in planar microwave devices, such as self-biased circulators. Cu doping is an effective method to tailor their anisotropy field and ferrimagnetic resonance (FMR) linewidth to meet the requirements for lowfrequency low-loss microwave devices. However, the regulation mechanism of Cu doping is still obscure, and its regulation effect is not optimized. Here, the magnetic and microwave properties of two groups of barium hexaferrites with site-controlled Cu doping are reported. The diffusion dynamics of Cu 2+ ions are comprehensively investigated, revealing significant differences in the concentration distribution and polycrystalline morphology, when comparing CuO as a reactant and sintering additive. The accumulation of Cu 2+ ions at grain boundaries contributes to the increase in coercivity, whereas the dispersion of Cu 2+ ions in crystallites leads to the decrease in the anisotropy field. Moreover, by introducing Cu 2+ ions into the interstitial positions of the lattice, barium hexaferrites with a narrow FMR linewidth of 303 Oe and a high remanence ratio of 0.82 are achieved. These results represent the lowest FMR linewidth reported in polycrystalline hexagonal ferrites and prove the great technological value and commercial potential of Cu-doped barium hexaferrites for next-generation planar microwave devices.

Effect of Oxidant Concentration on Properties of Ferrite Films by Spin-Spray Deposition

“…Theoretically, the crystallographic plane (222) orientation should be denoted as the [111] crystallographic direction orientation. To confirm the existence of this (222) crystallographic plane preferential orientation, which will result in a triangular grain shape, the micro-morphologies of all samples were characterized using FESEM and are presented in Figure 3.O 2− To evaluate the degree of orientation, the predominance of the (222) facet was quantified using the Lotgering factor [29][30][31]: denotes the factor for those with a random orientation. XRD peaks within the 2θ range of 20°-70° were employed for this calculation.…”

“…Key parameters such as the lattice constant (a), average grain size (D) calculated using Scherrer's formula, and the deposition rate of the thin film calculated by dividing the film thickness by 20 min are summarized in Table 1. To evaluate the degree of orientation, the predominance of the (222) facet was quantified using the Lotgering factor [29][30][31]:…”

Enhancing temperature stability of Ce: RIG films Faraday rotation through magnetic sublattice control

“…So, the increase in damping corresponds to an increase in the octahedral iron ratio, while a decrease in damping corresponds to an increase in the tetrahedral iron ratio, thereby validating the accuracy of In 3+ or Ga 3+ doping positions. Other studies have also utilized variations in FMR linewidth or damping to demonstrate the substitution of iron content [36,37].…”

Contribution of Magnetization Mechanisms in MnZn Ferrites with Different Grain Sizes and Sintering Densification

“…In summary, among the studies focusing on magnetic properties, composition, additives, sintering processes, and the spectra of complex permeability [27][28][29][30][31][32][33], few have delved into the contribution of magnetization mechanisms in MnZn ferrites as a function of grain size and its relationship with the sintering temperature. This research presents an exploration of the magnetization mechanisms in MnZn ferrites at different sintering temperatures, discussing the findings in conjunction with the fitting results of permeability spectrum dispersion.…”