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We have studied the reliability of a near-field transducer (NFT) embedded in a magnetic recording slider used for heat-assisted magnetic recording (HAMR) in hard disk drives with a linear velocity of 20 m/s. The NFT head structure and the disk are separated by an air film of 2 nm thickness. In this article, the magnetic write width and amplitude of the written magnetic signal on the disk are used as a “health monitor” for the reliability of the NFT under long-term thermal exposure. The results show that the reliability of the NFT head structure sharply decreases with increasing temperature of the NFT but depends only slightly on the media temperature. [ABSTRACT FROM AUTHOR]

The spacing between the flying head and the rapidly rotating disk in hard disk drives continues to decrease in order to grow the areal density. In heat-assisted magnetic recording (HAMR), the spacing control complexity is compounded by the additional protrusion resulting from the laser heating. Compared to the writer induced and thermal fly-height control protrusion, the near-field transducer (NFT) protrusion is a faster and more local protrusion that requires new HAMR-specific spacing control techniques. In this paper, we will review the simulation and experimental studies which shed light on both the steady-state and transient characteristics of the NFT protrusion. Simulation analysis reveals the scale of the protrusion and its effects on spacing control. Experimentally, we have demonstrated a novel technique to characterize the NFT protrusion and assist in setting the spacing for each HAMR head. Based upon the knowledge gleaned from characterization, compensation schemes have been developed. Some of the schemes have already been successfully demonstrated. [ABSTRACT FROM AUTHOR]

Heat assisted magnetic recording (HAMR) has the potential to deliver higher storage areal density beyond 1 Tb/in2. A laser is integrated in the flying read/write head to heat up the magnetic media using a near field transducer (NFT). A large portion of the laser energy is absorbed inside the head, resulting in elevated temperature around the NFT. Thermal protrusions of different magnitudes and time scales occur after turning on the laser. These laser heating-induced protrusions must be characterized for each head and compensated in HAMR drives. In this paper, a magnetic recording-based method is proposed to perform in situ protrusion measurements and assist in setting the write spacing. This method has been successfully demonstrated on the spinstand and implemented into HAMR drives. [ABSTRACT FROM AUTHOR]

In this paper, some issues concerning the reliability of heat-assisted magnetic recording (HAMR) media are highlighted. The large roughness of the grain structure originates from a surface energy mismatch between the FePt grains and the graphene-like segregant material. A simple roughness model, based on interfacial energies, is proposed that can quantitatively predict media grain structure and roughness. The thermal behavior of the disk lubricant is reviewed both experimentally as well as theoretically using molecular dynamics (MD) and density functional theory (DFT). The lubricant film can be subjected to evaporation and oxidation, both of which follow an Arrhenius reaction rate. MD also predicts that the disk carbon overcoat can undergo structural changes under thermal transient exposure in the nanosecond time frame, and Raman imaging performed on a disk zone that was HAMR written shows small but unequivocal changes, consistent with an increase in carbon sp^2 cluster size. [ABSTRACT FROM PUBLISHER]

To achieve disk drive recording densities greater than one terabit per square inch, future head-media spacings (HMSs) will need to be less than 7 nm. This will place severe demands on the metrology tools used to measure the thickness and topographies of the contributors to the head-media spacing. Here, we first review some of the metrologies used for characterizing overcoats, lubricants, and topographies and discuss some of the limits that will make it difficult to achieve a sub-7-nm HMS. We next show new results for measuring lubricant redistribution on disk surfaces after contact with a small pad on the slider and present a new method for determining wear rates of these slider contact pads. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation would be well suited to predict the physics of molecularly-thick lubricants on magnetic disk surfaces. The difficulty in defining suitable interatomic potentials, as well as the requirement for large computing power, makes this type of study difficult. Treating the lubricant film in the framework of fluid dynamics has proven a much better way to model its behavior. This paper describes a full numerical model of lubricant moguls and ripples formation using finite difference analysis. We demonstrate that both moguls and ripples result from slider-induced air shear. Ripples tend to form at higher disk speed and narrower slider width, whereas moguls are seen at lower speed and larger slider width. Both moguls and ripples are enhanced for thicker lubricants, higher waviness, and lower flying heights. Ripple instabilities that were predicted earlier using a stability analysis are also quantitatively confirmed using this numerical model. [ABSTRACT FROM AUTHOR]

We report here an excellent field emission performance from periodic patterned graphene nanomesh (GNM) field emitter. A simulation of the relationships between external electric field and the local electric field enhancement on the GNM edges was conducted to optimize the parameters of the nanostructure. Experimental results revealed that the gate driving voltage was as low as 20 V. This kind of emitters also shows good field emission stability. It is expected that the GNM introduced here will generate impacts for the further advancement of graphene field emission devices in emerging technologies and applications. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations of the lubricant ripple formation when the slider flies on the track. We quantified the impact of ripple amplitude on slider flying height modulation (FHM). Comparisons were made between experimental observations and a previous modeling study where rippling was shown to be caused by slider-induced air shear modulation. We confirmed our model predictions and demonstrated conditions under which ripple formation is enhanced or reduced. [ABSTRACT FROM AUTHOR]