Materials Development for Thermally-Assisted Magnetic Recording Media
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Materials Development for Thermally-Assisted Magnetic Recording Media C.F. Brucker and T.W. McDaniel Seagate Technology, 47050 Kato Road Fremont, CA 94538, U.S.A. ABSTRACT
We have carried out a combined experimental and computer simulation study to specify and identify candidate films to support high areal density, thermally-assisted magnetic recording. The motivation of this work is to utilize the enhanced writability of very high coercivity materials that thermal assistance can provide. Media with high coercivity (and anisotropy Ku) are known to be essential to achieve a sufficiently high ratio of KuV/kBT necessary to maintain magnetic stability at temperature T in media switching units (grains; single domains) of volume V. Nominally, we expect V ∝ D−3/2, where D is the medium bit density per unit area in recording. A micromagnetic recording simulation tool with a capability of representing realistic grain size distributions, temperature-dependent magnetic properties, and spatially-varying imposed temperature distributions was employed to study the interplay of thermal and magnetic field gradients in the recording process. In addition, a simple LLG-based thermomagnetic switching model supplemented the micromagnetics model. We fabricated improved Co/X multilayer media for recording evaluation, and performed standard materials characterization. RATIONALE FOR HYBRID RECORDING
Data storage technology has been advancing rapidly for several decades, with magnetic recording in particular having accelerated its rate of advancement several times in the past dozen years. With annual compound growth rates of areal density (count of “bits” per unit area on the recording medium’s surface) rising above 100% in the last few years, magnetic recording technology in rigid disk drives (RDD’s) appears to be approaching fundamental physical limits for the first time in its one hundred year history [1]. This situation has prompted accelerated research and development to modify the course of the technology’s evolution, spurring renewed interest in perpendicular recording, and more recently drawing attention to novel approaches of patterned media and hybrid recording [1]. This paper deals with storage media materials development for hybrid recording. We define “hybrid recording” as an alternative approach to conventional magnetic recording in which thermal-assistance of the record and/or playback processes is invoked to improve system performance. Sometimes optical irradiation of media has been used to impart heating, but other means of introducing thermal energy can be envisioned. Nevertheless, the term hybrid recording has most often been understood to mean a merging of aspects of magnetic and optical recording. The writing process in hybrid recording is essentially thermomagnetic recording very similar to that employed in magneto-optic recording [5]. One uses the temperature-dependence of the recording medium’s magnetic properties to advantage for enabling high quality magnetic recording in a situation where the magnetic writing hea
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