Flexible Polymer/Ferrite Composites for Q-Band Millimeter-Wave Applications

The technological demands of the modern world motivate the development of new materials and manufacturing techniques for millimeter-wave electronics. In this work, we demonstrate mechanically flexible magnetic composites for use at Q-band millimeter-wave frequencies, particularly in the upper 5G spectrum. Flexible magnetic composites of the polymer polydimethylsiloxane (PDMS), and micro/nano particles of either barium ferrite (BaM), strontium ferrite (SrM), or yttrium iron garnet (YIG) are fabricated in molds backed by glass slides using a facile, cost-effective, and low-temperature deposition process. Material characterization uses vibrating sample magnetometry (VSM) for static magnetic hysteresis parameters and rectangular waveguide measurements for complex permittivity and permeability from 33 to 50 GHz. VSM results show the BaM and SrM composites are self-biased, meaning that they have an internal remanent magnetic field that establishes a ferromagnetic resonance (FMR). The waveguide measurements affirm FMR in BaM around 47.2 GHz and in SrM around 46.5 GHz, but the FMR of the YIG is below the measured frequency range.