Screen-Printable, Self-Biased SrM/PDMS Composites for Integrated Magnetic Microwave Devices

This work introduces a material and method for high-volume, low-temperature, screen printing of self-biased magnetic films made from a composite of M-type strontium ferrite SrFe12O19 (SrM) particles and polydimethylsiloxane (PDMS). The magnetic particles are aligned under a dc magnetic field, while the PDMS is cured at 75 degrees C, making this fabrication process compatible with semiconductor and printed-circuit-board substrates. Aligned composites with estimated SrM particle volume percentages of 14 vol.%, 20 vol.%, and 27 vol.% are fabricated, as well as an unaligned 14 vol.% composite for comparison. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to examine the structure and composition of the composites. Furthermore, vibrating sample magnetometer and ferromagnetic resonance (FMR) measurements are performed to determine their dc and ac magnetic properties. Results show that the aligned composites have magnetic textures between 1.47 and 1.95, crystalline anisotropies between 1860 and 1960 kA/m, FMR frequencies of 45.5-45.9 GHz, and FMR linewidths between 3400 and 3500 Oe, indicating the potential for these materials in self-biased, non-reciprocal device applications. The analysis identifies that increased particle loading and better particle alignment may further improve these films by decreasing the linewidth.