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. CrO
2
particles in coated medium were perpendicularly oriented by this method. Achievement of the orientation is evident from magnetic measurements :
Hc\perp=700
Oe,
Hc\parallel=600
Oe,
O. R. \perp=3.22
,
O. R. \parallel
=0.71, and from high