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A novel hard disk lubricant IDL2 was synthesised by reacting sodium 4-((2,2-dimethyl-1,3-dioxolan-4-yl)methoxy)phenoate with hexachlorocyclotriphosphazene, followed by treatment with 1H,1H-perfluoro-3,6,9-trioxatridecan-1-ol in the presence of sodium hydride and subsequent hydrolysis using sulfuric acid. The chemical structure of IDL2 was confirmed by proton nuclear magnetic resonance (1H NMR), phosphorus-31 (31P) NMR spectroscopy and mass spectrometer. The thermal property of IDL2 was analysed using thermal gravimetric analysis (TGA) and it shows better thermal stability than two commercial lubricants Z-DOL and Z-Tetraol with two and four terminal hydroxy groups, respectively. IDL2 was found to have comparable hydrophobicity to commercial lubricants Z-DOL, A20H and Z-Tetraol with water contact angles in the range of 78 – 85°, revealing that IDL2 has analogous surface energy to these commercial lubricants. IDL2 exhibits comparable friction coefficient to A20H and Z-Tetraol, but much lower than Z-DOL. More interestingly, it has a much high bonding ratio when compared with commonly used commercial lubricants under the same testing conditions due to the presence of two polar hydroxy groups, which enhance the interaction between lubricant and substrate. These promising properties of IDL2 show that it would be very potential for real application as a hard disk drive lubricant. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Novel cyclotriphosphazene based lubricant oil ( Lube-PN ) for heat-assisted magnetic recording media was synthesized by reacting hexachlorocyclotriphosphazene with pentafluorophenol, followed by treatment with a hydroxy-terminated perfluoropolyether in a high yield. Its chemical structure was confirmed by 1 H and 31 P NMR. Its properties including viscosity, thermal stability, tribology, laser resistance as well as mobility behaviour on the hard disk surface were investigated. The thermal properties of Lube-PN were analysed using thermogravimetric analysis, and the thermal aging results showed that the about 80% of Lube-PN was retained even after heating at 300 °C for 8 h. The Lube-PN also exhibited comparable bonding ratio, friction coefficient, moderate mobility and better laser resistance than commercial perfluoropolyether based lubricant oils.

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 ${K_{u}}$ 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.

In this paper, we focus on ways to optimize the manufacturing of products whereby the final product performance is measured by the aggregated performances of its components. Specifically for hard disk drives, the final recording capacity is the aggregate of the components’ achievable capacities. As is the case for hard disk drive, a drive normally has a targeted capacity such that if it falls below its target, it will be rejected or downgraded. Similarly, products achieving well above the target will still be sold at the target capacity. At both extremes, it results in loss of profits. Hence, the aim of this paper is to propose a novel selective assembly strategy which can improve profitability by reducing the variation of components in the final product assemblies and achieving the target performance. As our case study, the assembly of hard disk drive (HDD) is used to demonstrate its feasibility in real manufacturing settings. Two theorems, (1) discarding theorem and (2) binning theorem, are formulated to guide the selective assembly strategy. They provide the rules for discarding inferior components before assembly to ensure the quality of the starting population and the rules for selecting matching pairs of components to prevent producing over qualified product. The improvement in component utilization rate over random binning is guaranteed by the two theorems.

Through a novel temperature measurement method, this paper studies the lubricant film property subjected to heat-assisted magnetic recording (HAMR) laser heating. The material characterization of lubricant film under HAMR ultra-fast heating rate and ultra-short heating period condition has been compared with that after conventional thermal heating. The relationship of lubricant degradation and decomposition with the heating rate and heat duration and the reaction of the lubricant with the metal used for the temperature sensor has been studied and discussed.

This paper investigates the effects of laser irradiation on hard disk lubricants of Z-Tetraol and DEPH. Through the study of different Heat Assisted Magnetic Recording (HAMR) laser effects on hard disk lubricant components including different perfluoropolyether backbones, hydroxyl end-group and cyclotriphosphazene end-group, suitable components for HAMR application are discussed.

Currently, the areal density grow in HDD still depends on the reduction of grain number per bit. In order to have less SNR penalty, it has to scale more on the track density rather than the linear density. This work proposed to insert an additional servo recording layer between data recording layer and SUL of conventional PMR media. With high quality continuous servo signals, the dedicated servo recording system has better servo performance than the conventional embedded servo for the same servo mechanics. This guarantees the high track density requirement of magnetic recording system.

The recent advancements in the development of new functionalized nanostructured materials (i.e., multilayers and nano-composites) have pushed the film thickness into sub-nanometer range. The design and optimization of the final properties of these materials to meet the demands of their final application completely depends on an appropriate combination of film thickness, composition and microstructure. Measuring such film properties on this kind of ultra-thin film poses a significant challenge to the capabilities of current analytical characterization tools. In particular, significant challenges exist in the depth resolution of depth profiling techniques, such as XPS and AES. Sampling depth and sputter ion energy as well as Zalar rotation were widely believed to be the significant factors to affect the depth resolution. In this work, we studied the effects of these factors to the depth resolution on one type of typical ultra-thin film material that was the topic of many recent research and development works, namely ultra-thin diamond-like-carbon film. Furthermore, this work focused on finding out the sensitivities of these variables to the depth resolution. In doing so, we hope to find out the limit of improvements on the depth resolution on these very important depth profiling techniques.