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The dedicated servo media (DSM) is the conventional perpendicular magnetic recording (PMR) media with an inserted servo recording layer between the data recording layer and the soft underlayer. By using the conventional PMR media as the reference, the design consideration on the layer structure, the preparation, the magnetic properties, the microstructure, including the $c$ -axis orientation and the growth of the layers, the surface roughness, and the recording performance for the DSM are reported. [ABSTRACT FROM AUTHOR]

The perpendicular magnetic recording (PMR) in hard disk drives is approaching its physical limitation. The emerging technologies, such as heat assisted magnetic recording and microwave assisted magnetic recording have been proposed to record on magnetic media with thermally stable smaller size grains at higher areal density (AD). However, in the media fabrication, achieving well-isolated small size of grains is more challenging than obtaining high Ku material as recording media. Reducing the number of grains per bit is a major path for keeping AD growth of PMR in recent years. To minimize the SNR penalty at a smaller grain number per bit, pushing more on track density is the right approach. With the 2-D magnetic recording (TDMR) readers for inter-track interference cancellation, the off-track read capability is improved significantly for allowing a narrower track read. In the drive working environment, when the external vibration or other mechanical disturbance happens during the writing process, it creates more track squeeze at adjacent tracks and leaves a very narrow track at some locations of the track. When the track width is narrower than the squeeze to death width in the 747 curve, it causes hard failure in the channel. To solve the track squeeze problem, this paper proposes to add an additional magnetic recording layer in between the data recording layer and the soft underlayer of conventional PMR media. This additional recording layer is used to record servo information only. The continuous positioning error signal is able to improve the servo performance and to provide the real-time monitoring of the positioning error. When it is under bad servo conditions, the writing process can be stopped to avoid nontolerable track squeeze. The continuous servo signals are designed to be of moderate intensity at very low frequency, and its impact on data signal has been minimized. The linear density gap between the dedicated servo media and the conventional PMR media is able to be controlled within 3%. As the dedicated servo system keeps only around 100 wedges of track ID and sector ID at the data layer, the surface area saving at the data layer can break even in capacity. The dedicated servo technology together with TDMR readers is the key technology to achieve ultrahigh track density during both writing and reading processes. [ABSTRACT FROM AUTHOR]

Microstructural investigations of granular perpendicular recording media based on stacked CoPt-alloy layers were carried out using high-resolution transmission electron microscopy (HRTEM). In the structure investigated, a thin layer of CoPt with high Pt concentration was inserted to meet the thermal stability requirements at higher densities. The increase in the coercivity and nucleation field of the sample observed for the insertion of a thin layer of CoPt (3 nm), and the decrease beyond this critical thickness has been explained based on HRTEM studies. HRTEM results indicated that the insertion of thicker CoPt layer causes stacking faults and the presence of fcc phase in the CoCrPt layers on the top. The number of stacking faults and the fcc content in grains depend on the thickness of CoPt layer, indicating that the observed changes in magnetic properties arise due to the microstructural changes. [ABSTRACT FROM AUTHOR]

New methodology to obtain reliable correlation between magnetic cluster details measured using magnetic force microscopy (MFM) and noise in perpendicular recording media is reported. In addition to the ac demagnetized state, which is often studied by several researchers, magnetic clusters were examined at two other magnetic states of the recording medium to obtain details on thermally unstable and relatively nonreversible clusters that would increase noise and bit-error rates. The proposed method was employed to study magnetic clusters of media samples fabricated at different conditions. Measurements on various samples demonstrated that the MFM can be used to understand the thermally unstable and irreversible clusters in a perpendicular recording medium. A direct correlation between the signal-to-noise ratio of the medium measured using spin-stand and magnetic cluster details from MFM images is obtained. The trend can also be used to understand and distinguish the source of noise (such as writing issues or the media microstructure issues). [ABSTRACT FROM PUBLISHER]

Perpendicular recording media technology faces limitation in the writability of media with high anisotropy. Therefore, alternative methods are sought to overcome this problem. Heat-assisted magnetic recording may give rise to high areal densities, but the technological process will take time. We have studied methods to improve the writability in perpendicular recording media using crystalline soft underlayer (C-SUL) materials with fcc(111) texture. One of the recording media designs consists of a simple insertion of C-SUL material between the nonmagnetic intermediate layers, thus providing a path for magnetic flux during the writing. In the alternative methods, part of the nonmagnetic intermediate layer material was replaced with C-SUL material. Overwrite improvement was observed in both the cases, indicating that the C-SUL material will play a major role in improving writability in recording media. [ABSTRACT FROM AUTHOR]

The planarization of patterned recording media is essential to overcome the "flying height reduction" and "flying instability" of the head-slider. This paper reports two planarization techniques; one by compressing a morphological smooth surface onto a low glass transition temperature TgUV curable polymer/material coated patterned sample, while the other employs spin coating to coat patterned disks. A roughness of 0.3 nm was achieved by planarization using compression of smooth Si onto 35 K PMMA (heated above Tg to decrease its viscosity). It was also found that decreasing the spin speed from 5000 rpm to 1000 rpm improves the filling of grooves using spin coating of hydrogen silsesquioxane (HSQ) decreasing the height difference between the filled groove region and the land region from about 6 nm to 4 nm. Initial investigation using compression of smooth Si onto diluted HSQ also shows a decrease of roughness as dilution increases from 50.0% to 66.6%. Both techniques were applied in the planarization of a UV curable resist. The results show that about 1 nm is observed between the patterned and unpatterned regions using only spin coating. However, with compression using a flat mold, no height difference on average is observed. [ABSTRACT FROM AUTHOR]