Some Factors Influencing the Choice of a Medium for Magnetic Recording

Abstract

No other single factor contributes so much to the ultimate performance of a magnetic recording system as the recording medium itself. Within the last three or four years, many papers have described the performance of magnetic recording systems but none has given much attention to the correlation between the magnetic properties of the recording medium and the performance of the system. It is the purpose of this paper to show how some of the performance characteristics of magnetic recording systems depend on the magnetic characteristics of the recording medium. The most important single magnetic characteristic of the medium for good high frequency response is high coercivity. High retentivity is necessary for high output voltage at the frequency of maximum response. However, low retentivity is desirable not only from the viewpoint of reducing crosstalk but also from that of improving the response at the higher audiofrequencies relative to the response at the frequency of maximum response. The ratio of coercivity to retentivity is proposed as a figure of merit for estimating or predicting the frequency response of a medium when used with a specific magnetic recording system. The limitations imposed by the magnetic properties of the medium on the design of magnetic heads and magnetic recording systems are also discussed. The problem of modulation noise and its relation to the Barkhausen effect is emphasized because this may impose a serious limitation on the use of certain magnetic recording media which seem to be excellent in all other respects.