Co/Pd Multilayer Based Recording Layers For Perpendicular Media
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Co/Pd Multilayer Based Recording Layers For Perpendicular Media Dmitri Litvinov∗, Thomas A. Roscamp1 , Timothy Klemmer,
Mei-Ling Wu, J. Kent Howard, and Sakhrat Khizroev Seagate Research, Pittsburgh, Pennsylvania 15203 1 Roscamp Engineering, Woodlane Park, Colorado 80866
ABSTRACT The results of the experimental study of CoX/Pd multilayer based recording layers for perpendicular recording media are presented. The perpendicular magnetic recording media with multilayer recording layers and high moment soft underlayers were deposited by magnetron sputtering. It is shown how a favorable microstructure of the multilayer films can be achieved by the use of the appropriate buffer layers. The effects of boron addition to the cobalt layer in a multilayer recording layer is described. The feasibility of the aging process that leads to the reduced exchange coupling in the multilayer recording layer, is demonstrated. It is shown that boron addition to the cobalt layer accelerates the aging process. INTRODUCTION As the storage industry ramps the areal bit densities at increasingly higher rates, thermal instabilities in recording media begin to manifest themselves[1]. Perpendicular recording technology[2] while being technically close to conventional longitudinal recording and the least difficult technology to make the transition to if necessary[3, 4, 5], addresses the issue of thermal stability for areal bit densities exceeding 100Gbit/in2 [6]. Several candidates for the perpendicular media recording layers are being considered. Hexagonal single layer CoCr-based alloys are among the strongest candidates due to a wealth of knowledge about material properties accumulated over the years using these alloys for longitudinal media. The major drawback in using hcp Co alloys is the difficulty in achieving the high remanent squareness, preferably equal to one. Remanent squareness of less than one leads to substantial DC noise and potential thermal instabilities. L10 phases of CoPt, FePt, etc. suffer from the lack of knowledge of how to control the microstructure and magnetic properties. These highly attractive materials due to their high magnetic anisotropy can play an important role in the future magnetic recording technologies if the mentioned above technical difficulties are resolved. An alternative approach is to use Co and Co-alloy based multilayers[7, 8]. In this set of materials, the magnetic anisotropy is controlled by interfacial effects between Co and Pt or ∗
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Pd non-magnetic (but highly polarizable) spacer layers. The multilayers form an attractive class of materials since they exhibit high remanent squareness and easily controlled magnetic anisotropy with both aspects being critical for the thermal stability. EXPERIMENTAL DETAILS The perpendicular magnetic recording media used in this study were deposited by magnetron sputtering onto ceramic glass substrates. The following general perpendicular media structure was utilized [substrate/buffer/soft underlayer/buffer/multilayer/overcoat]. The medi
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