Heat-Assisted Recording: Advances in Recording Integration

Abstract

Differences between heat-assisted magnetic recording (HAMR) and conventional perpendicular magnetic recording (PMR) for signal processing of the written track by one and two reader multisensor magnetic recording (MSMR) are explored using spinstand measurements. Tracks written with HAMR heads are shown to have more curvature compared with those written with modern PMR writers. We introduce two signal processing techniques in order to determine the merits and explore the recording physics tradeoffs for this complex system. To first order, we see twice as much bit error rate (BER) gain for the HAMR written track—on readback—using two reader MSMR, than the PMR. This difference we assign to the lower electronic signal-to-noise (SNR) ratio for the HAMR written track. In order to replicate practical conditions, we stress the MSMR system by applying increased adjacent track squeeze and displacing the two readers from the center of the track. Under these conditions we can resolve differences between the PMR and HAMR systems. Increased adjacent track squeeze appears to trim the broad and curved track edges, until the on-track signal starts to degrade. Increased offset of the readers from the center of the track offers improved the media (spatial) SNR, but we fail to harvest all those gains into BER across the range. We hypothesize that this is due to increasing distortion, a combination of track edge noise and reading of the encroaching tracks.