Problems in magnetic recording on relatively thick media

The decay of a magnetic scale signal due to repeated reading is measured, and its relation to the magnetic properties of the recording material is studied. A sine-wave signal of wavelength 0.2 mm is recorded on Cu-Ni-Fe alloy plates 0.3 mm thick. The signal is read by a flux-sensitive multigap reading head. It is found that the penetration of the recorded signal into ordinary Cunife (Cu:Ni:Fe = 60:20:20; Br= 5 kG, Hc= 370 Oe) is only a few μm. Both the "magnetic wear" and the depth of the signal penetration has been improved over Cunife by reducing the Br/Hcratio down to about 5.