High permeability and low loss easy-plane ferrites with multi-ions doped for miniaturized 5G antennas

Ferrites are the desirable candidates for antenna substrates due to their high permeability and low magnetic loss. However, such excellent magnetic properties cannot be maintained in the GHz band due to the Snoek limit. Here, we report a BaCo1.8Zn0.2Fe16O27 (CoZnW) ferrite prepared by doping multiple ions at the lattice (Zn ions) and grain boundaries (Bi/Ca/Si/V ions) of conventional BaCo2Fe16O27 (Co2W) ferrites, achieving a high permeability of 3.3, low magnetic loss tangent of 0.05, and a high figure of merit (FOM=mu ' Qf = 66) at 1 GHz, which is much better compared to the previous reports. Moreover, the dimensions of the antenna deploying the multi-ions doped CoZnW are only 52 % of those deploying conventional commercial materials (Fr4) because of its high permeability and low loss. Such a high permeability is attributed to the enhanced saturation magnetization and the reduced anisotropic field achieved by Zn ions modulation. The low magnetic loss is attributed to the reduced damping of domain wall motion and the refined grain size achieved by Bi/Ca/Si/V ions modulation. Our work not only provides a promising candidate for 5G antennas but also uncovers a physical mechanism for the modulation of magnetic properties of ferrites.