MAGNETIC VISCOSITY OF RECORDING MEDIA

Time dependence of the magnetisation, or 'magnetic viscosity' is a well established phenomenon in magnetic recording media. On a practical basis magnetic viscosity is related to the phenomenon of print-through and the frequency dependence of the coercivity. The latter factor has a bearing on the use of the coercivity in materials characterisation and also has implications for the ultimate minimum size of switching volume usable in recording media. The physical origin of magnetic viscosity is reviewed, along with the relationships to the above factors. Also, recent work on the determination of switching volumes is described.