A perpendicular orientation of a coated particulate medium by an AC-demagnetization process

A new perpendicular magnetic orientation method for coated particulate medium has been studied in order to resolve two problems : "self-demagnetization accompanying re-disorientation" of particles and "surface roughening" in conventional DC orientation method applied to coating a particulate medium in a low viscous state. These two phenomena are discussed in terms of a stabilization of magnetization energy in a perpendicular demagnetization field. AC demagnetization is used to erase residual magnetization just after AC magnetic orientation. For these two purposes a magnet is used which has a pair of pole pieces with graded edges and is operated at 50 Hz. CrO2particles in coated medium were perpendicularly oriented by this method. Achievement of the orientation is evident from magnetic measurements :Hc⊥=700Oe,Hc∥=600Oe,O. R. ⊥=3.22,O. R. ∥=0.71, and from high