Effect of Recording Layer Thickness on Read/Write Performances of Co/Pd Multilayer Perpendicular Magnetic Recording Media

Masaru UCHIDA  Naoki HONDA  Kazuhiro OUCHI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E83-C   No.9   pp.1522-1529
Publication Date: 2000/09/25
Online ISSN: 
DOI: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Selected Papers from the 4th Asian Symposium for Information Storage Technology)
Category: 
Keyword: 
perpendicular recording media,  recording layer thickness,  loop slope,  recording performance,  Co/Pd multilayer film,  

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Summary: 
The medium noise of single-layer perpendicular recording media is known to be suppressed by reducing the magnetic domain size and achieving a higher squareness ratio (Mr/Ms = SQ) in the perpendicular M-H loop. The media with smaller domain sizes exhibit a small slope at Hc in the M-H loop due to exchange de-coupling between adjacent grains, which requires a sharp head field to acquire high recording performances. Reduction of the medium thickness would be effective for recording as only a sharp head field near the head surface could be used. Thus, the effects of reduced recording layer thickness in single-layer perpendicular recording media on read/write performances were investigated using Co/Pd multilayer media with a small loop slope having thickness, δ, of 46, 22 and 10 nm, and with a steeper loop slope having δ of 40 and 10 nm. It was found that the recording performance on small loop slope media could be improved in terms of signal level by reducing the recording layer thickness, which indicated that the recording on the media was sensitive to the recording head field. The results in the simulation analysis were similar to those obtained experimentally, indicating that the change in recording layer thickness could be mainly regarded as that in the head-medium spacing. Thinner media with steeper loop slopes could acquire a narrower dipulse width. The recording resolution of the present media, however, was determined under the influence of the domain structure and the size. Finally, for media with small loop slopes, the same SNR of 38 dB at 100 kFRPI was obtained for thicknesses of 22 and 10 nm, which was larger than that for a thick medium of 46 nm thickness by 8 dB. For both the steep loop slope media, the obtained SNR was 35 dB at 100 kFRPI.