Synthesis and Characterization of High-Purity Yttrium-Iron-Garnet Nanowires Inside a Porous Silicon Membrane by the Sol–Gel Method

Recently, nonmetallic ferromagnetic nanowires (NWs) have been implemented in porous templates. Such composite substrates are used to design various microwave, magnetic, and electronic devices. To synthesize ferrite NWs, the precursor solution consists of either magnetic nanoparticles (NPs) dispersed in a polymer as a surfactant or metal nitrates, which are used in a sol-gel method. The magnetic properties of ferrite NPs change significantly due to their large surface-to-volume ratio. For these NPs, the saturation magnetization is reduced due to the superparamagnetism phenomenon. In this letter, we investigated the increase of the saturation magnetization and the volume loading of synthesized yttrium iron garnet (YIG) NWs in a porous silicon membrane. To enhance the filling factor of the YIG NWs, multiple techniques are utilized, such as a permanent magnet, bath sonication, and vacuum suction. Our experiments show that in the sol-gel method using vacuum suction, the NWs loading factor can be greater than a 50%, as the purity of the YIG NWs increases to 98.2% by decreasing the precursor molarity (from 2 to 1 M), reducing the oxygen flow in the electric furnace (from 10-20 standard liters per minute to 5-10 SLPM) and increasing the magnetic stirring time (up to 24 h). The magnetic properties of the YIG NWs are investigated using a vibrating sample magnetometer.