Magnetic write field characterization in heat-assisted magnetic recording systems

Abstract

Magnetic write field is a critical factor in determining the quality of the magnetic write transitions, which determine the linear density (LD) limit in heat-assisted magnetic recording (HAMR). We introduce a reversed DC band approach as a simple, no extra-hardware-Required technique in a spin-stand to assess the magnetic write field ( ) contributions, independently in an HAMR system. Heads with different distances between near-field transducer and writer pole, and media with and without soft magnetic under layer were characterized. The estimated result strongly correlates with LD and signal-to-noise ratio, which agrees with previous modeling studies. These results give insight into the head/component required to optimize the HAMR’s system performance. The technique provides qualitative ranking of magnetic write fields and recording temperature, as well as laser operating current at Curie temperature for head/component designs.

Track width measurement in heat-assisted magnetic recording systems using the cross-track DC noise method

“…The noise at the track edge is being amplified by a small angle of the free layer. [23][24][25][26][27] The written track width is revealed by measuring the distance between the noise peak locations of positive and negative DC fields.…”

“…The test track is carried out using a single reversed DC track for both positive and negative polarities, as described in Ref. 23 [Kampun et al 2020]. To determine the noise peak locations, the magnetic grain randomness of the track was measured as a function of cross-track positions.…”

“…op While increasing the I op used for reversed DC erase, the noise peak location of the cross-track noise profile shifts away from the track center. 23) The polarity of the written DC track on the media determines the shifting direction of the noise peak. When the track was written by a reversed DC track with negative polarity, the noise peak was observed on the left side of our tester test system, as shown in Fig.…”