In current magnetic recording media the signal-to-noise ratio needed for high-density recording is achieved by statistically averaging a large number of weakly interacting magnetic grains per recorded bit. Traditional engineering of magnetic media to achieve higher recording densities involves reducing the grain diameter and film thickness, but this approach is increasingly limited by instabilities due to thermal fluctuations. This phenomenon is thought to limit potential recording densities and is commonly referred to as the "super-paramagnetic limit." This article discusses this problem in the context of traditional recording media and new thin-film media and structures that push back the super-paramagnetic limit.
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