Permeability spectra of Co2Z hexaferrite compacts produced via a modified aqueous co-precipitation technique

Co₂Z hexaferrite materials possess intrinsically high permeability, zero field ferromagnetic resonance values (∼1 GHz), and have their magnetic orientation in the plane perpendicular to the c-axis. These characteristics make these materials practical for applications in low to mid ultra-high frequency and L-band microwave device designs. Due to the relatively large size of elements operating within these bands, it has become important to produce large amounts of Co₂Z type hexaferrite materials. A modified co-precipitation method has been proposed to produce scalable quantities of high quality Co₂Z hexaferrite particles, at ∼24 g/L. These particles have been thoroughly characterized by vibrating sample magnetometry (VSM) and X-ray diffraction (XRD) with regard to phase purity and magnetic properties. After formation and subsequent ball milling, to achieve single domain particles on the order of 0.5–2 um, particles were oriented and pressed into compacts inside a rotating field to ensure magnetization in plane. Samples then underwent VSM, XRD, and scanning electron microscopy to determine the orientation effect. In addition, the complex permittivity and permeability of these samples were measured as a function of applied field and processing conditions. The results show strong orientation in these compacts making them practical for a variety of device applications.