Nano-granular metal/insulator multilayer for reader shielding materials

We have developed materials with high resistivity and permeability. It cons ists of multilayered magnetic metal/insulator films such as CoFe/Al2O3, NiF e/Al2O3 and NiFe/SiO2. The thickness of each layer is around 1 mn. This fil m consists of metal granules around run size covered with insulator as evid enced by using transmission electron microscopy (TEM). The multilayer film CoFe/Al2O3, showed a resistivity of more than 10 m Omega cm and a coercivit y of the hard axis was between 80 and 240 A/m, and saturation magnetization was higher than 0.9 T. The permeability of this film was around 250 up to GHz level. In this study, the film structure offering the highest resistivi ty and permeability was 20 to 40 layers of CoFe(1.3-1.5 nm)/Al2O3(1.0-1.2 n m) bilayer. Nano-granular high-resistivity materials are therefore appropri ate for using as head shielding material.