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Transition from fourth to fifth generation wireless technologies requires a shift from 2.3 GHz to Ka-band with the promise of revolutionary increases in data handling capacity and transfer rates at greatly reduced latency among other benefits. A key enabling technology is the integration of Ka-band massive multiple input–multiple output (m-MIMO) antenna arrays. m-MIMO array elements simultaneously transmit and receive (STAR) data providing true full duplexing in time and frequency domains. STAR requires, as a central component, the circulator. However, conventional circulators are bulky and prohibit the engineering of Ka array lattices. A necessary innovation calls for the integration of device-quality Ka-ferrites with wide-bandgap (WBG) semiconductor heterostructures allowing for system-on-wafer solutions. Here, we report results of a systematic study of pulsed laser deposited (PLD) barium magnetoplumbite (BaM) films on industrial compatible WBG semiconductor heterostructures suitable for operation in Ka-band circulators. We demonstrate successful PLD growth of BaM films on WBG semiconductor heterostructures. BaM films that show device quality performance in structure, epitaxy, and magnetic properties were realized for BaM/MgO/AlN/SiC(X). Film properties include bulk-like values of magnetic anisotropy field, Ha ∼16.5 kOe, and saturation magnetization, 4πMs ∼ 4.2 kG. Ferromagnetic resonance linewidth values are competitive and comparable with device design goals for insertion loss. Only heterostructures where SiC substrates have Si-polar surface showed superior properties. These results define a path for integration of magnetodielectric materials on wide bandgap heterostructures for self-biased devices essential to implementing millimeter-wave m-MIMO array and the enormous potential it offers to 5G technologies.

Polycrystalline samples of Z-type hexaferrites, having nominal compositions Ba3Co2+xFe24-2xMxO41 where M = Ir 4+ , Hf 4+ , or Mo 4+ and x=0 and 0.05, were processed via ceramic processing protocols in pursuit of low magnetic and dielectric losses as well as equivalent permittivity and permeability. Fine process control was conducted to ensure optimal magnetic properties. Organic dispersants (i.e., isobutylene and maleic anhydride) were employed to achieve maximum densities. Crystallographic structure, characterized by X-ray diffraction, revealed that doping with Ir 4+ , Hf 4+ , or Mo 4+ did not adversely affect the crystal structure and phase purity of the Z-type hexaferrite. The measured microwave and magnetic properties show that the resonant frequency shifts depending on the specific dopant allowing for tunability of the operational frequency and bandwidth. The frequency bandwidth in which permittivity and permeability are very near equal (i.e., ~400 MHz for Mo 4+ (x), where x=0.05 doping) is shown to occur at frequencies between 0.2 and 1.0 GHz depending on dopant type. These results give rise to low loss, i.e., tan δ # /ε & = 0.0006 and tan δ ' /µ & = 0.038 at 650 MHz, with considerable size reduction of an order of magnitude, while maintaining the characteristic impedance of free space (i.e., 377±5W). These results allow for miniaturization and optimized band-pass performance of magnetodielectric materials for communication devices such as antenna and radomes that can be engineered to operate over desired frequency ranges using cost effective and volumetric processing methodologies.

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