3D inkjet printing of ferrite nanomaterial thin films for magneto-optical devices

A novel method of preparing magnetic ink belonging to the class of ferrofluids which contains magnetic particles with a polar surface-active agent is disclosed. The magnetic material belongs to the group known as magnetite (Fe₃O₄), typically to those with γ-Fe₂O₃ and their likes. Ni-Zn ferrite and Mn ferrite inks were prepared using this method. The inks have a PH value and total dissolved solute of about 6.3, 3.78 mS and 5.9, 4.2 mS respectively, and a viscosity of about 7 cPa, 7.4 cPa respectively. The saturation magnetization of Mn ferrite ink at 300K was 62 emu/cm³. This lower value of the saturation magnetization of Mn ferrite compared to the bulk is because of the shell-core structure of the surfactant coated ferrite particles. The inks were used to prepare various thicknesses ranging from 0.5um to 20um of both Ni-Zn ferrite and Mn ferrite thin films. The surface morphology of the thin film was observed using Atomic Force Microscopy (AFM), showing a compact, dense and relatively smooth film. The microstrip transmission line permeameter approach was used to extract the permittivity and permeability of the thin film samples within the frequency range of 10MHz-1GHz. A relative permeability of 2 was measured. The developed ink and thin film are promising for future magneto-optical applications.