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It has been suggested that magnetization switching dynamics at low energy damping could result in severe write field loss at high data rate for perpendicular recording. To experimentally study the possible dynamic effect and to investigate write field loss at extremely high data rates for today's state-of-the-art perpendicular write heads, recording tests at data rates beyond 2 Gbits/sec-ond are performed...
This article reports the effect of varying the damping in different individual sections of the perpendicular recording head (like the yoke, pole and soft underlayer (SUL) regions) affects the head switching speed. Two head designs were used: the shielded head and monopole head design. The head model used in this paper divided the head into five regions: a) soft underlayer, b) tip, c) confluence, d)...
In this paper, 3D modelling of the interaction between lubricant droplets on the slider surface and air flow within the head/disk interface of disk drives is presented. A very strong coupling between the lubricant droplet motion and air flow is discovered for ultra low flying slider design. The lubricant droplet is driven to migrate towards the slider's trailing edge by a net effect of air shearing,...
Potential use of FeCo alloys in high moment inductive writer heads is limited by large values of magnetostriction and coercivity. Recent work shows that metallic seed layers, including Ru, improved the soft properties of sputter-deposited FeCo by reducing the grain size of the deposited FeCo films. We carried out a series of experiments to investigate the effect of Ru, Ta and NiFe seed layers and...
Recently, an efficient spin-stand based imaging technique for viewing magnetization patterns written on hard disk platters has been developed. This technique requires the intersymbol interference (ISI) removal from raw read-back images. This removal can be accomplished by using the response function characterization of giant magnetoresistive heads. The precise measurement of the head response function...
In this paper, the recording performance of two types of media are compared by calculating the head field distribution of an 80 nm wide write pole in conjunction with a soft magnetic underlayer. The maximum effective field was inclined 15deg from the perpendicular axis. The effective head field gradient was a maximum when the head field was inclined 35deg from the perpendicular. Composite media have...
L10-FePt is a promising material for ultra high density magnetic recording media due to its high magnetocrystalline anisotropy (Ku). However, the switching field (Hsw) of the L10-FePt particle is too large to write by the currently used write head. Hard/soft stacked media are proposed to solve this problem. Recently, we demonstrated that the coercivity of isolated FePt particles can be reduced by...
All-metallic giant magnetoresistive (GMR) sensors in a current-perpendicular-to-plane (CPP) geometry are attractive candidates for future high-density recording sensors due to their low intrinsic resistance. With increasing recording density the cross-sectional area of CPP sensors (such as TMR or GMR sensors) must also decrease, resulting in a rapid increase in sensor impedance unless the RA product...
We introduced vapor corrosion inhibitor (VCI) into a disk drive to improve the resistance of the components to corrosion in repeated condensation cycles. VCI also significantly reduced the defect smears in the disks during accelerated life test. VCI is well known to cover up exposed metal surfaces. Thus the first means by which a VCI prevents corrosion is by forming a hydrophobic adsorbed film over...
In this study, we investigated the effect of molecular structure of the PFPE (per-fluoro-poly-ether) lubricant upon the adhesive force between the head and disk. In particular, we compared the head-disk adhesive forces experienced when lubricants of the same backbone terminated with a functional group at one and at both ends, respectively, were used.
The head disk interface spacing in current disk drives is controlled by thermal protrusion of a small heater coil near the read write element of the slider body. By adjusting the power to the heater coil, the clearance can be very accurately adjusted. In addition to controlling clearance, the amount of interference can be adjusted when going into contact. In this paper, we investigate the slider dynamics...
To achieve ultra-low flying height, we have developed a thermal flying-height control (TFC) slider that carries a micro-thermal actuator. Using the actuator, the magnetic spacing of these sliders can be controlled in-situ while the drive is operating. The previous component-level prototype had insufficient actuator characteristics. Therefore, the purpose of this research is to improve the actuator...
In this paper, we propose a quasi-static approximation of track-seeking motion. The track-seeking performances of four different air bearing surface (ABS) designs are numerically investigated by the quasi-static approximation and the CML Dynamic Simulator.
In this study we report variable footprint shapes indicating recording pole instability. We extend the spin-stand "footprint" measurements to also evaluate recording pole instability. The observed recording pole instability causes degradation of the system performance and should be avoided. The switching between these states is random and occurs after high frequency head excitation. The...
We have developed a method to measure HKS from the playback waveform from a specific recording pattern.In the current high-density perpendicular magnetic recording system, the head air-bearing surface (ABS) to soft under-layer (SUL) surface, or so called head keeper spacing (HKS) is one of the key parameters that affect both writer field strength as well as playback process. Here we describe the principle...
We present a direct method for comparing longitudinal and perpendicular recording that does not depend on any additional assumptions. All drives are built with the same ABS. For the same change in pressure, all heads experience the same change in spacing. Thus, the performance can be compared directly as a function of pressure without any measurement of spacing.
Transition curvature is a significant factor in limiting the densities that can be achieved using perpendicular recording. In this report, the transition curvature of a written track is extracted solely from measurements on a spin-stand. Both signals waveforms and background media noise waveforms were captured. By numerical post-processing, the transition shape can be determined by referencing it...
Continuous thin film magnetic media have long been used in the data storage industry but densities above 1 Tbit/in2 may not be possible due to onset of the superparamagnetic limit. Patterned media have been suggested as a possible means to exceed this limit, and it has been shown that irregularities in the shape and size of magnetic islands due to imperfections in the patterning process introduce...
We perform fully integrated micromagnetic simulations of patterned recording media to optimize the recording process.Fully integrated simulation contains the induction coil in the write head, the yoke, the pole tips, shields, return pole, recording media and magnetic soft under layer (SUL). The magnetization behavior of the media is calculated by taking into account the interactions and back interactions...
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