Pigment-to-binder loading effects in Ba-ferrite coatings

Particulate media utilizing small, platelet-shaped particles of Ba-ferrite are of great interest for magnetic recording applications because they offer the potential for developing low-cost media with perpendicular magnetic anisotropy and enhanced performance 1,2. When properly designed, they proved excellent short wavelength response and moderate temperature coefficients of their magnetic properties³A significant drawback derives from their low saturation magnetization, which is about 20 percent lower than that of the gamma iron oxides. A way to circumvent this deficiency is to increase the pigment-to-binder ratio (p/b) in the coating, an approach believed to be applicable to the barium ferrite pigments without degrading the physical characteristics of the coatings, on account of their small particle size and their smooth platelet morphology. In this study, we investigated the effects that increased p/b ratios have on the magnetic properties of the barium ferrite coatings. We found that, under certain circumstances, increasing the p/b ratio may result in some stacking of the platelets, which in turn increases the coercivity of the coating significantly. These changes in magnetic properties can be quite large and must be carefully considered in designing Ba-ferrite media for specific applications.