Sooyoul Hong

Perpendicular recording heads for extremely high density recording

It has been shown that excellent recording performance can be achieved at high areal densities using a probe head with square pole tip and perpendicular media with soft under-layers In order to maintain the writability at even narrower track widths and minimize the side writing effects at large skew angles, finite-element modeling has shown that trapezoidal pole tip is needed In this work we present the general head design and magnetic recording performance of our third generation advanced probe heads with trapezoidal pole tips.

Overview of Fly Height Control Applications in Perpendicular Magnetic Recording

The ability to control head-to-media spacing through a heating element has many technical implications. Properly applying this capability can significantly improve bit error rate (BER) performance in perpendicular magnetic recording (PMR). It also calls for the development of techniques associated with clearance control. A good touchdown detection method and an accurate measurement of spacing change are essential for proper clearance control. This paper analyzes the potential performance improvement through the application of clearance reduction during writing and reading. Touchdown detection methods and spacing calculation accuracy will also be analyzed

Stress Induced Permanent Magnetic Signal Degradation of Perpendicular Magnetic Recording System

Model scratches of the size found in hard disk drives are produced under controlled conditions at a series of applied loads on both longitudinal magnetic recording (LMR) media and perpendicular magnetic recording (PMR) media using a diamond tip. The scratches are created at low speed, eliminating thermal considerations from the interpretation of the media response. Nanoindentations are produced as well. The scratches and indentations are characterized by atomic force microscope (AFM), magnetic force microscope (MFM), and also by the same magnetic reader and writer used in an integrated hard disk drive (HDD). A comparison of the response of PMR and LMR media shows the PMR media to have larger scratches and greater magnetic signal degradation than LMR media for a given scratch load. The extent of magnetic damage, as measured by MFM, is greater than the extent of surface mechanical damage, as measured by AFM. Analysis of scratches using the HDD reveals that the magnetic damage is irreversible and permanent damage in magnetic layer, which is confirmed by cross section transmission electron microscope image. The experiments reveal the mechanism for magnetic scratch erasure in the absence of thermal effects. This understanding is expected to lead to improved designs for mechanical scratch robustness of next-generation PMR media.

Recording Performance Study of PMR Media With Patterned Tracks

Discrete track recording technology offers a potential advantage in reducing adjacent track erasure/interference. As nano-imprinting technology advances, fabrication of such media has been demonstrated. In recent years, discrete track recording has generally been viewed as one of the next promising technologies for areal density advancement. In this study, we evaluated the recording performance of PMR media with patterned tracks. To accurately assess the advantage of discrete track performance and compare with current continuous media, both recording performances were measured on one single track. The head flying height is monitored on the patterned and continuous media regions. At 100-nm data track width, patterned tracks show noticeably better signal-to-noise ratio and significantly lower adjacent track erasure compared with continuous media at the same track width. Such measured performance advantages are critical to increase track density beyond 300-400 ktpi

Dependence of sputtering power and soft underlayer on magnetic properties in CoCrPtO perpendicular recording media

In this paper, sputtering power dependence on magnetic properties and microstructure of CoCrPtO perpendicular recording media was examined. Also, change of magnetic properties of CoCrPtO layers on two different soft underlayers was investigated. As the oxygen gas ratio increases, coercivity (Hc) increases regardless of the variation of the sputtering power up to a certain critical oxygen gas ratio which depends on the sputtering power. Then, Hc drops sharply in all cases. The higher the power is, the higher the critical oxygen gas ratio is. As the oxygen gas ratio increases, exchange slope also decreases more rapidly at the lower sputtering power than higher power. The small grains of the size of /spl sim/7 nm with thick amorphous-like grain boundaries are observed in the media sputtered at the power of 75 W. It is considered that the selective oxidation of grain boundary is performed more effectively at low sputtering power. CoCrPtO layer on NiFeNb soft magnetic underlayer (SUL) showed higher Hc of 5000 Oe and well isolated grain in comparison with CoCrPtO layer on CoZrNb SUL. This difference of coercivity behavior may be associated with difference CoCrPtO layer on residual stress or surface roughness.

Reduction of adjacent track encroachment in exchange coupled composite media through soft magnetic layer with high Ku

Exchange coupled composite (ECC) media on the Al disk substrate with soft underlayer were fabricated with different anisotropy field ratios between hard magnetic and soft magnetic layers. The enhanced signal to noise ratio of about 2.5dB was obtained from ECC media having anisotropy field ratio of 3, which showed even narrow magnetic write width, compared to ECC media with anisotropy field ratio of over 10. Especially, ECC media with lower anisotropy field ratio of 3 exhibited much reduction in adjacent track encroachment (ATE). Micromagnetic modeling indicated that large negative nucleation field is crucial to the implementation of ECC media with lower dc noise and improved ATE. The main reason is, for soft magnetic layer with high saturation magnetization and low anisotropy field, the very wide write bubble occurring during dynamic recording process. It resulted in poor ATE performance, which agreed well with experimental data.

Role of Ag seed layer for CoCrPt/Ti perpendicular recording media

2 nm metal seed layers (M=Al, Cu, Ni, Cr, Ag, Mg, Fe, Co, Pd, Au, Pt, Mo, and Hf) were sputtered to increase coercivity (Hc) and anisotropy (Ku) of CoCrPt/Ti perpendicular recording media. Among them 2 nm Ag seed layer was very effective to increase Hc of (Co78Cr22)100−xPtx/Ti (x=14,20). However, the effect was more pronounced when (Co78Cr22)100−xPtx films became thinner. In addition α [=4π(dM/dH)Hc] decreased when the Ag layer was used. The film thickness below which the seed Ag layer was effective was reduced with decreasing Pt content. However, x-ray diffraction data showed that the Ag seed layer did not promote (002) texture of Ti and CoCrPt layers. In magnetic force microscope observations, domain size was reduced when the Ag seed layer was used. The reason for the higher coercivity of CoCrPt films with the Ag seed layer is thought to be due to change of exchange constant of the grains, for which the grain boundary area plays an important role. Effects of film thickness and Pt content can also be exp...

Optimization of perpendicular recording on exchange coupled composite media

Using micromagnetic modeling, the recording performance of exchange coupled composite (ECC) media with perpendicular heads was systematically studied. The simulations indicated that the switching field angular dependency of ECC media is similar to the continuous media switching behavior. By tuning the magnetic properties of the soft∕hard layers, it was found that a soft layer with high saturation magnetization and low anisotropy energy caused large dc noise and unfavorable Adjacent Track Erasure (ATE) performance in recording, which is mainly due to the small nucleation field. A quantitative optimization of ECC media was given. Recording with different head designs on ECC media was also evaluated and this showed that large head field gradients at both the trailing edge and track edges are crucial to the implementation of ECC media at high recording areal density.

Improved recording performance using side-shielded pole head in PMR drive

A recording performance for the side shielded pole head (SSPH) with trapezoidal pole tip is compared to a conventional single pole head (CSPH) with the SiO/sub 2/ dispersed double-layered perpendicular magnetic recording (PMR) media. The SSPH showed 3 dB higher SNR, 22.5% enhanced D/sub 50/, and about 10 dB better NLTS compared to the CSPH design. Noise analysis showed the SSPH had lower noise than the CSPH. The lower transition noise and better NLTS is attributed to reduction of transition jitter in SSPH. The perpendicular magnetic recording drive having a storage capacity of 80 GB/platter has been successfully demonstrated with SSPH. Finally, the on-track bit-error rate (BER) measured for 10 sectors of a linear density of 653.2 kb/in at 7200 rpm was about 10 /spl times/ 10/sup -6.7/ for the SSPH design, about two orders improvement over the CSPH design.

Effects of magnetic damping constant of the soft underlayer on SNR in double layered perpendicular magnetic recording media

The magnetic dynamics of a total recording system composed of a single pole head and a perpendicular recording medium with a soft underlayer was performed by a three-dimensional micromagnetic model. In this paper, the effect of the magnetic damping constant of the soft underlayer (SUL) on the signal-to-noise ration (SNR) was systematically studied for the case of abrupt change in head field. For this purpose, the different damping constants (/spl alpha/) of 1.0, 0.1, 0.03, and 0.01 were studied in a conventional SUL. In all cases, SNR rapidly decreased with decreasing /spl alpha/ of SUL. The longer range magnetic fluctuation in the SUL for smaller damping constant affects the shift of the transition region of the bits more. For comparison, we have shown SNR for the same media with a head field rise time was considered.