Time-dependent magnetic phenomena and particle-size effects in recording media

Particle size is very important in determining the behavior of magnetic recording media. Particles must be large enough to provide adequate stability against time-dependent magnetic effects; these effects are seen as a dependence of coercivity on the duration of field application, so that the coercivity relevant to long-term storage stability can be significantly less than that relevant to high-frequency writing. On the other hand, the need for high signal-to-noise ratios, narrow transitions, and smooth tape or disk surfaces dictates that particles be as small as practical. Optimum particles for high-density recording will represent a compromise between these conflicting requirements