YIG based broad band microwave absorber: A perspective on synthesis methods

[Display omitted] •Successfully synthesized YIG nanoparticles (NPs) by solid state (SS) and sol-gel (SG) methods to elucidate the effects of nanoscale finite size and their microwave absorption capabilities.•Microwave absorption reached as high as −28dB at 20GHz with a film thickness of 300μm for SG and −18dB for SS NPs.•These materials can be used for stealth technology. The fabrication of a thin layer of microwave absorber that operates over a wide band of frequencies is still a challenging task. With recent advances in nanostructure synthesis techniques, considerable progress has been achieved in realizations of thin nanocomposite layer designed for full absorption of incident electromagnetic (EM) radiation covering S to K band frequencies. The primary objective of this investigation is to achieve best possible EM absorption with a wide bandwidth and attenuation >10dB for a thin absorbing layer (few hundred of microns). Magnetic yttrium iron garnet (Y3Fe5O12; in short YIG) nanoparticles (NPs) were prepared by sol–gel (SG) as well as solid-state (SS) reaction methods to elucidate the effects of nanoscale finite size on the magnetic behavior of the particles and hence their microwave absorption capabilities. It is found that YIG prepared by these two methods are different in many ways. Magnetic properties investigated using vibrating sample magnetometry (VSM) exhibit that the coercivity (Hc) of solid-state NPs is much larger (72Oe) than the sol-gel NPs (31Oe). Microwave absorption properties were studied by ferromagnetic resonance (FMR) technique in field sweep mode at different fixed frequencies. A thin layer (∼300μm) of YIG film was deposited using electrophoretic deposition (EPD) technique over a coplanar waveguide (CPW) transmission line made on copper coated RT/duroid® 5880 substrates. Temperature dependent magnetic properties were also investigated using VSM and FMR techniques. Microwave absorption properties were investigated at high temperatures (up to 300°C) both for sol-gel and solid-state synthesized NPs and are related to skin depth of YIG films. It is observed that microwave absorption almost vanishes when the temperature reached the Néel temperature of YIG.