A novel method of preparing magnetic ink belonging to the class of ferrofluids which contains magnetic particles with apolar surface-active agent is disclosed. The magnetic material belongs to the group known as magnetite (Fe_3O_4),typically to those with γ-Fe_2O_3 and their likes. Ni-Zn ferrite and Mn ferrite inks were prepared using this method. Theinks 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 ofabout 7 cPa, 7.4 cPa respectively. The saturation magnetization of Mn ferrite ink at 300K was 62 emu/cm~3. This lowervalue of the saturation magnetization of Mn ferrite compared to the bulk is because of the shell-core structure of thesurfactant coated ferrite particles. The inks were used to prepare various thicknesses ranging from 0.5um to 20um ofboth Ni-Zn ferrite and Mn ferrite thin films. The surface morphology of the thin film was observed using Atomic ForceMicroscopy (AFM), showing a compact, dense and relatively smooth film. The microstrip transmission linepermeameter approach was used to extract the permittivity and permeability of the thin film samples within thefrequency range of 10MHz-1GHz. A relative permeability of 2 was measured. The developed ink and thin film arepromising for future magneto-optical applications.
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