P.A.A. van der Heijden

Measurement of Ga implantation profiles in the sidewall and bottom of focused-ion-beam-etched structures

Ga implantation during focused-ion-beam (FIB) milling of metallic magnetic materials for magnetic recording heads was examined using Auger electron spectroscopy (AES). The Ga concentration profiles were characterized in two directions: in the depth direction (parallel to the incident beam) and in the lateral direction (perpendicular to the incident beam). The sample for AES analyses in the depth direction was prepared by FIB etching of a plated Ni78.5Fe21.5 film surface. The AES depth profile showed a maximum implanted Ga concentration of ∼20 at. % at a distance of ∼15 nm, and the tail of the implantation profile reached more than 100 nm. The sample for the lateral direction analyses was prepared by cutting a cross-sectional specimen out of the air-bearing surface of a working recording head. The lateral profile showed a maximum implanted Ga concentration of 47 at. % at the surface, with a lateral implantation depth of ∼10 nm. These results were compared with results predicted by a Monte Carlo implantatio...

A perpendicular write head design for high-density recording

In this paper, we discuss a single-pole perpendicular head design and process that is suitable for densities of the order of 100 Gb/in/sup 2/. The single-pole write head was integrated with a narrow-track bottom spin valve reader. The design uses a single-turn coil to generate magnetomotive force in the head. Because of the very short yoke length that is achieved by using a single-coil turn, this writer design has a very low head inductance. Low magnetic impedance of the head makes it suitable for high data rate writing. Using the finite element model (FEM), the head geometry was optimized to write on media with coercivity (H/sub c/) of 5000 Oe. Because of the very efficient head structure, a write current below 100 mA was sufficient. As trackwidths are reduced, the field contours at the media show significant curvature, resulting in written-in transition curvature. Because of the very small yoke structure, no degradation of low-frequency amplitude up to /spl plusmn/90 Oe of external field is observed.

Comparison of perpendicular and longitudinal magnetic recording using a contact write/read tester

We have performed longitudinal and perpendicular magnetic recording measurements using a contact write/read tester, which scans a magnetic recording head in contact with the recording media. Our tester has a demonstrated positioning resolution of <5 nm. Perpendicular transitions in the range 125-425 kfci were recorded on double-layer perpendicular media with a high moment soft underlayer. The perpendicular bits were imaged using both a giant magnetoresistance (GMR) read head on the contact tester and using magnetic force microscopy (MFM). Longitudinal bit transitions with linear densities in the range 25 to 725 kfci were recorded, and the signal-to-noise ratios of both the perpendicular and longitudinal systems were measured.

Current-perpendicular-to-plane multilayer sensors for magnetic recording

We investigated current-perpendicular-to-plane giant magnetoresistance multilayer (CPP-ML) sensors with an active region of (1.0-nm CoFe/1.8-nm Cu) /spl times/ 15 nm. These sensors would allow a shield-to-shield spacing of less than 50 nm. Square CPP-ML devices ranging in size from 120 to 365 nm on a side have been fabricated and tested. In this paper, we focus on the magnetotransport properties of the 140 nm devices, which were measured at room temperature. The average device characteristics were found to be R/sub max/=1.0 /spl Omega/, R/sub min/=0.81 /spl Omega/, DR=191.1 /spl Omega/, and DR/R/sub min/=23.7. These values were measured by using a four-point probe geometry; the data were not corrected for lead or contact resistance and no current crowding was observed. After correction for buffer and seed layer resistances, the magnetoresistance had an intrinsic DR/R/sub min/ value of 55.6%. Our measured results are in good agreement with values obtained with a simple two-current series resistance model. We demonstrate that our CPP-ML structures are viable candidates to replace current-in-plane spin valves as the next generation magnetic recording readback sensor.

Thermal stability of NiMn spin valve heads

The thermal stability of NiMn-based spin valves was studied both at the coupon level and in full read/write heads. In the coupons, the blocking temperature distribution showed no component below 150/spl deg/C. As a result, the exchange field at elevated temperature was found to increase with time (because of improved chemical ordering of the NiMn layer), and irreversible losses in the /spl Delta/R/R response were observed only above 250/spl deg/C (because of layer interdiffusion). If a 10% drop in /spl Delta/R/R amplitude is used as a criterion to calculate time to failure, the NiMn heads should have several hundred years of lifetime at 150/spl deg/C operating temperature. Full read/write heads showed linear response with read-back amplitudes above 2 mV//spl mu/m at 6-mA operating current. In contrast to most other giant magnetoresistance heads, the output of the head remains the same after heating with a high bias current and degrades only with the shorting of the stripe. All these properties make NiMn superior to other antiferromagnets for spin valve head applications.

Perpendicular recording near 100 Gb/in/sup 2/

Theoretical analyses have projected perpendicular recording capable of achieving ultimate areal densities greater than longitudinal recording systems. For perpendicular recording to supplant longitudinal recording, laboratory demonstrations will need to be made which intercept or exceed the areal densities achieved by state-of-the-art longitudinal recording demonstrations. Recent demonstrations have come close to eliminating the gap between these technologies. In this paper, recording experiments at areal densities in the 60 to 100 Gb/in/sup 2/ range will be described. It will be shown that the head field from conventional single-pole writers is not well localized to the data track and that if the media do not have sufficiently high nucleation thresholds, this fringe field will gradually erase data on the adjacent track if the track pitch is too aggressive. Extension of this technology to densities of the order of 1 Tb/in/sup 2/ will require heads that reduce the extent of the fringe field without sacrificing available on-track field.

Asymmetric focused-ion-beam trimming of longitudinal and perpendicular write heads

In this paper, we focus on head trimming techniques based on a asymmetric trimming process, whereby only one side of a write pole is FIB trimmed to achieve the target width. We use this technique for longitudinal and perpendicular HGA-level head trimming.

Inverted spin valves with irmn biasing layer

Inverted IrMn-based spin valves (ISV) were fabricated with the aim of low thickness/high output dual spin valve applications. Optimized structures exhibit the following characteristics: H/sub exch/=750 Oe, R/sub sq./=18.5 /spl Omega//sq., /spl Delta/R/R=7.5% and T/sub b/=250/spl deg/C with IrMn thickness as low as 75 A. The blocking temperature distribution, however, exhibits nonzero components from 150/spl deg/C onwards. Accordingly, accelerated sheet films lifetime experiments and current heating on full read/write heads show that partial rotations of the pinned layer occur well below T/sub b/. These structures therefore appear to be insufficiently stable for disk-drive applications.

Evaluation of transition curvature in perpendicular magnetic recording

In this paper, we report a detailed experimental study on the effect of the transition curvature on the read-back signal and magnetic recording performance.

On-wafer production monitoring of GMR spin valve pinned layer and free layer properties

Introduction While electrical and magnetic properties can be tracked on unpatterned coupons, direct measurement on patterned wafers is essential to determine actual device pmperties, to measure the device changes during processing, and to compare patterned device properties to unpattemed coupons. Spin valve pmperties can be studied using unshielded test structures [1,2]. Basic measurements include resistance, AFUR, sensitivity, asymmehy, bias, and interlayer coupling.