High-throughput nanomanufacturing of synthetic antiferromagnet-polymer nanoparticles with high magnetic moment, very low remanence, and high magnetic susceptibility for biomedical applications

A high-throughput top-down nanomanufacturing approach for making metal-polymer nanoparticles with tunable magnetic properties using nanoimprint lithography is reported. The nanoparticles comprise of a layered structure that includes a Co/Ru/Co synthetic antiferromagnet (SAF) and a polymethyl methacrylate (PMMA) or a hydrogen silsesquioxane (HSQ) layer. The Co/Ru/Co structure deposited by magnetron sputtering was tuned to achieve antiferromagnetic coupling between Co layers, desired magnetic susceptibility, and saturation magnetization. Ultrahigh density positive tone thermal nanoimprint lithography molds designed to maximize the depth and minimize the thickness of imprint trenches in nanoimprint resist (PMMA or HSQ) were fabricated. The molds were used to pattern large arrays of 200 nm x 200 nm, 400 nm x 400 nm, and 600 nmx 600 nm SAF nanostructures with superparamagneticlike magnetic characteristics. The nanostructures were released from the wafers into an aqueous suspension by dissolving the sacrificial underlayers, Cu for SAF/PMMA nanoparticles and PMMA for SAF/HSQ nanoparticles. Published by the AVS.