Media Roughness and Head-Media Spacing in Heat-Assisted Magnetic Recording

Heat-assisted magnetic recording involves the transfer of energy to the recording medium via optical means. To enable high areal density, the recorded track must be smaller than the diffraction limit of focused light, which is accomplished by using a near-field transducer (NFT) with a corner or peg with small dimension. Energy transfer using such a transducer is a near-field effect, and therefore is highly sensitive to the spacing between the NFT and the medium. Since the recording medium has some surface roughness, there will be a variation in the NFT-to-medium spacing and this will impact the amount of energy transferred from the NFT. We model the effect of Gaussian surface roughness on NFT energy transfer and predict surface temperature variations for a rough surface. In addition, we illustrate how changing the head-medium spacing changes the impact that roughness has on surface temperature variation. We combine these modeled predictions with spinstand measurements of recorded data and conclude that the effect of media roughness results in only limited temperature excursions above the nominal recording medium temperature.