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M.-C. Cyrille,
F. Dill,
Jay Li, R. Fontana,
M. Pinarbasi,
A. Baer,
J. Katine,
A. Driskill-Smith,
W. Jayasekara,
D. Mauri,
M. Ho,
K. Mackay,
Ching Tsang
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ABSTRACT: As the areal density of magnetic recording increases well beyond 100 Gb/in<sup>2</sup>, the critical dimensions of recording heads continue to shrink at a rate of 15%-30% per year. Read sensors with 100 nm physical read widths are being routinely fabricated using undercut resist images and solvent-based liftoff processes. However, because standard liftoff processes using undercut photoresist images have reached their limits and cannot be performed reliably below 100 nm, sensor stabilization with a hard magnet contiguous junction is compromised because of induced variations in junction profile and hard magnet geometry. Furthermore, poor liftoff can induce fencing and excessive read gap topography leading to side reading and poor sensor performance. An alternative sensor patterning approach is proposed based on chemical mechanical polishing (CMP) and no-undercut resist images to define the read sensors critical dimensions. Ultra-narrow giant magnetoresistive (GMR) read heads have been successfully fabricated with physical read widths in the 20-80 nm range and using various sensor designs: Current in-plane (CIP) GMR, current perpendicular to the plane (CPP) GMR, and CPP tunnel magnetoresistive (CPP-TMR) sensors
IEEE Transactions on Magnetics 11/2006; · 1.36 Impact Factor
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ABSTRACT: The in-stack stabilization of unshielded and shielded magnetic tunnel junction (MTJ) sensors have been studied experimentally by quasi-static and recording tests as well as theoretically by micromagnetic modeling. Results showed the viability of in-stack stabilization over a range of design and material conditions. Performance tradeoff studies and design optimization results led to the fabrication of MTJ read heads with good magnetic stability and high readback sensitivity.
IEEE Transactions on Magnetics 02/2004; · 1.36 Impact Factor
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ABSTRACT: Self-heating of GMR sensors is investigated experimentally and
numerically. We measure the thermal conductivity of the read gap layers
independently and model heat transfer at the air bearing surface using
the results of molecular scale simulations. Temperature profiles
obtained by simultaneous application of scanning probe and electrical
resistance thermometry agree well with numerical simulation
results
IEEE Transactions on Magnetics 08/2001; · 1.36 Impact Factor
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C. Tsang,
M. Pinarbasi,
H. Santini,
E. Marinero,
P. Arnett,
R. Olson,
R. Hsiao,
M. Williams,
R. Payne,
R. Wang,
J. Moore,
B. Gurney,
T. Lin, R. Fontana
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ABSTRACT: We have successfully demonstrated magnetic recording at areal
densities as high as 12 Gb/in<sup>2</sup> at a data rate of 14~15 MB/s
using separate spin-valve read heads and narrow pole-tip inductive write
heads on low noise Co alloy thin film disks. In this work, the nominal
target densities were 350 Kbpi×34 Ktpi. To make these densities
possible, large signal-to-noise gains were attained with the use of high
performance spin-valve read heads and low noise thin film media. At the
same time, very narrow track write heads were designed and fabricated by
extending conventional photolithographic techniques. Finally, small
magnetic spacings between the head and the disk were attained with low
flying ABS designs and improved head and disk surfaces. Recording tests
showed satisfactory writability and large readback signal of around 2
mV/μm. The 50% rolloff densities were as high as 10 Kfc/mm, while the
write and read trackwidths were as narrow as 0.7 and 0.5 μm
respectively. An overall assessment of the parametric recording results
indicated an areal density capability of at least 10 Gb/in<sup>2</sup>.
This projection was confirmed by error rate testing with an EPR-4
channel, where very low ontrack errors of 10<sup>-10</sup>~10<sup>-9
</sup> were achieved at 315~380 Kbpi. Furthermore, squeeze measurements
revealed well-defined 747 behavior with offtrack maxima at 0.7~0.8 μm
trackpitch. The product of linear and track densities for the write and
read head combinations tested indeed showed that an areal density of
11~12 Gb/in<sup>2</sup> has been achieved
IEEE Transactions on Magnetics 04/1999; · 1.36 Impact Factor
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ABSTRACT: The planar top down process reported by Bullock et. al. [1] for the fabrication of 1Mbit/cm<sup>2</sup>bubble memory devices [2] uses no spacer between the garnet surface and the AlCu metallization layer. The presence of this metal-garnet interface does not alter the magnetic properties of the epitaxial film and does result in a favorable reduction in generate current amplitudes. During the time-temperature cycles of the bubble device fabrication sequence, the changes in anisotropy, static coercivity, and the dynamic properties of films with this AlCu interface do not differ from observed changes in the material parameters of films having a first oxide buffer layer. Generate current threshold amplitudes are reduced by 30% when the spacer layer is removed. Successive temperature anneals at 375°C, the maximum temperature in planar process, decrease the generate current threshold value. This effect is identified with a reduction reaction which removes O 2 from the garnet surface at the film - AlCu interface.
IEEE Transactions on Magnetics 12/1981; · 1.36 Impact Factor
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ABSTRACT: The Texas Instruments 1 Mbit bubble memory device is fabricated in a 1 cm<sup>2</sup>area using 1.8 μm bubble material, a 6.75 μm by 7.5 μm cell size and 1 μm minimum permalloy features. The device architecture is block replicate. The device is organized into two identical 512 Kbit blocks each with 300 loops and 2049 storage locations per loop and each with an individual detector and generator. Design features include a set of generate, swap, and replicate gates compatible with planar processing, double period elements in the input and output tracks, and 15 μm period chevron expander columns in the detector. Device processing employs a planar, top-down sequence [1] to eliminate step coverage, plasma etching of AlCu leads, and direct step on wafer 10X projection printing for critical photolithography. Operating margins for packaged devices at 100 KHz, 62 Oe peak triangle drive are 14-18 Oe with current requirements of 13 mA-swap, 60 mA-replicate, 100 mA-generate, 4 mA-detect. The processing and gate designs of this 1Mbit device have been scaled to a smaller cell size, 4.75 μm by 5.25 μm, with a favorable reduction in operating current requirements.
IEEE Transactions on Magnetics 10/1980; · 1.36 Impact Factor
