Yoshiaki Kawato

Single-pole/TMR heads for 140-gb/in/sup 2/ perpendicular recording

Single-pole writers and tunneling magnetoresistive (TMR) readers for 140-Gb/in/sup 2/ perpendicular recording were fabricated and their recording performance was tested. Data erasure, which is observed as write instability in a repeated read-write operation, can be suppressed by combining a laminated pole and low throat height. Fe-Co/Ni-Cr laminated film was used to reduce the remanent magnetization of the main pole after patterning. Narrow track writers with a 120-nm-wide trapezoidal pole showed a good write ability of 30 dB or more in overwrite for media with high coercivity of up to 7 kOe. Also, negligibly small skew writing was confirmed. TMR heads with a sensor width of 85 nm and a head resistance of 250 /spl Omega/ showed approximately 30 dB of head signal-to-noise ratio (SNR). A potentially higher SNR with a higher operating voltage was suggested from a measured output versus sensing current curve. Calculations showed that the side reading was suppressed in a side-shielded design. A 10% amplitude width of the microtrack profile of a 100-nm-wide reader was reduced from 198 to 162 nm by applying the side shields.

Design and read performance of GMR heads with NiO

GMR heads with NiO/NiFe/Co/Cu/NiFe films have been designed, fabricated, and their read performance was tested. Calculations showed that output was reduced significantly when the exchange coupling field on the pinned layer was smaller than 200 Oe due to tilting of the magnetization of the pinned layer. When the pinned layer of NiFe(1 nm)/Co(1 nm) was used, the coupling field from NiO was 360 Oe which would be large enough to ensure the full output. The readback waveform of the fabricated head was noise-free and well biased. The obtained output was about six times as large as that of conventional AMR head. When the sensing current was increased, the output increased linearly up to the current density of 20 MA/cm/sup 2/, while the peak asymmetry was not affected much by the current. The output increased linearly with the read width, except for small dead zones at both of the track. The microtrack profile was symmetric, reflecting the symmetric magnetization configuration of the free layer without the medium field.

Fabrication process for a trapezoidal main pole for single-pole-type heads

We investigated the fabrication processes used for single-pole-type heads for perpendicular recording. To solve the problem of side write/erase on adjacent tracks, it is necessary to develop a trapezoidal main pole for single-pole-type heads. We therefore proposed two different fabrication processes: (1) a process using electroplating and ion milling and (2) a damascene process using reactive ion etching and chemical mechanical polishing. We made the trapezoidal main pole using the damascene process. An evaluation showed that using a single-pole-type heads with a trapezoidal main pole solved the side write/erase problem. There was also no problem with the writing performance of the heads. To make a narrower track (less than 250-nm wide), we optimized the process conditions.

Study on the write-field profile and intensity of narrow-track-width SPT head

The effects of the structure of a single-pole-type (SPT) head and the underlayer thickness on the write-field profile and intensity were examined by computer calculation. The results demonstrated the possibility of achieving a strong write field even with a thin underlayer in the case of narrow-track-width SPT. The shorter throat height enhanced the maximum write-field intensity without a great change of the write-field profile. We also proposed a new, tapered SPT head suitable to address the sidewriting issue for drive integration.

Current progress of single-pole-type GMR heads for perpendicular recording

We studied several proposals to address the problems encountered when single-pole-type giant magnetoresistive (SPT-GMR) heads are applied to an actual recording system. The first area of problems was regarding side erasure when there is a head skew. We fabricated a trapezoid-shaped main pole using a focus-ion-beam trimming or using a new wafer-processing technique and examined their write performances and their effects on reducing side erasure. The second area of problems concerned the stray field robustness of SPT-GMR heads when combined with a double-layered perpendicular recording medium. We tried to optimize the robustness and write performance by changing the width of a yoke in the main pole or by positioning a shield above the main pole. The stray field robustness and write performance were adequate in both cases, but a tradeoff relationship exists between both performances.

Fabrication processing of a trapezoidal main pole of single-pole-type heads

Summary form only given. The perpendicular recording system is considered as one of the most promising techniques to increase the areal density of hard disk drives. However, there is a side write/erase problem to adjacent tracks due to the skew angle of hard disk drives. A trapezoidal main pole of a single-pole-type head is required to improve this problem (S.E. Lambert and B.A. Lairson, PMRC 2000 digest 24aA-2, pp. 131-132, 2000). In this study, we investigated fabrication processing of the trapezoidal main pole.

Simulation of the write field for T-shaped pole heads

The write field distributions of T-shaped pole heads are presented. The maximum head field in the medium plane for T-shaped heads was larger than that for conventional structure heads. However, the field from the edges of the upper pole is not negligible for the T-shaped heads. As a result, neighboring bit patterns may be affected. To decrease the edge field, it is effective to make the throat height longer and recess the edges of the upper pole from the air bearing surface. Actual T-shaped heads were fabricated and their characterizations were investigated. The results agreed with simulations for longer throat height and for the recessed pole edge effect.

Perpendicular recording heads for areal densities over 100 Gb/in/sup 2/

Perpendicular recording with sufficient thermal stability has great potential for next-generation recording with areal densities over 100 Gb/in/sup 2/. One of the biggest problems for single-pole writers is head-induced erasure, such as erase-after-write This erasure is due to the high remanent magnetization of the main pole. We fabricated single-pole writers with a domain stabilization technique to reduce the remanence, and highly sensitive tunneling magnetoresistive (TMR) readers for 100 Gb/in/sup 2/ perpendicular recording.

Single-pole writer instabilities dependent on the pole-tip geometry

In this paper, we describe our experimental demonstration that the single-pole writer instabilities dependent on the pole-tip geometry. The instability of these writers is strongly dependent upon the throat height, which is defined as the distance between the flared point of pole tip and the air-bearing surface.

Large anisotropic magnetoresistance in ternary NiFeX films for magnetoresistive heads (abstract)

Highly sensitive magnetoresistive heads are required for magnetic disk drives with large areal density. Films with large anisotropic magnetoresistance are among the promising candidates for this purpose. In this work, the effect of third elements, X (Au, Pt, Ag, Cu, Pd, Co, Ru, ZrO2), to Ni80Fe20 alloy on anisotropic magnetoresistivity (Δρ) and other magnetic properties is examined with varying third element composition. Ternary films were deposited by rf sputtering on Ta seed layers. The thicknesses of ternary films were 5–20 nm which were determined by the x-ray reflectivity method. The value of Δρ for ternary films increases when Au, Pt, Ag, Co, and ZrO2 are added. On the other hand, Δρ decreases when Ru is added. Considering the application for the magnetoresistive (MR) head, low ρ0, low Hk, and low Bs are required except for large Δρ. The value of Δρ for Ni74Fe19Au7 film with the thickness of 10 nm is 0.65 μΩ cm which is 20% larger than that for Ni80Fe20. The values of Hk, λ, and Bs for Ni74Fe19Au7 a...