Stitch,
Here's a late 1996 article on the CPP-GMR (Current Perpendicular to the Plane) sensor developed by the folks at Livermore.
GIANT RESULTS FROM SMALLER ULTRAHIGH DENSITY SENSOR
llnl.gov
...The performance of the CPP-GMR sensor is a significant improvement over conventional GMR sensor design. Stearns' design has the GMR multilayers rotated 90 degrees so that the current flows perpendicular to the plane of the sensor. Because the signal from the CPP-GMR sensor is inversely proportional to its cross-sectional area, the signal actually increases as the sensor is scaled to higher and higher densities (and smaller sensor size). This scaling provides great manufacturing cost advantages for the future.
There are additional advantages to the CPP-GMR architecture. Conventional GMR sensors require shielding to be placed around the sensor for protection from stray flux, and the shields must be electrically isolated from the sensor. The extra parts and related design effort affect sensor size and cost. On the other hand, the Laboratory's CPP-GMR sensor is well integrated into the design of the magnetic head: it uses the "write" poles of the magnetic head to serve as shields for the sensor and as conductors for the magnetoresistive
current. As a result, the sensor conductors, the shields, and the inductive write poles are all integrated into a single structure to simplify the design, manufacture, and cost of the magnetic head.
Industrial Collaboration
After hearing about the potential for the CPP-GMR sensor, Read-Rite Corporation of Fremont, California, one of the world's leading supplier of magnetic heads, became an industrial collaborator with the Laboratory and has been working closely with the team to bring the product to market. The first results of this collaborative work included modifying the design to produce a linear sensor response, a
conventional practice in commercial manufacturing, and devising a self-aligning process for multilayer manufacturing, which will greatly drive down manufacturing complexity and costs. Together the two groups are currently developing fabrication sequences and designing tools to use in manufacturing the sensor. The CPP-GMR sensor will be able to function over a range of information storage densities, spanning from the current state-of-the-art at approximately 1 gigabit/in.2 (1
gigabit/6.4 cm2) which is at the size limits of magnetic disk drive technology. To scale up to the sensor's upper density limits requires no change in the magnetic head architecture. The CPP-GMR sensor will be more robust and more sensitive as it is scaled down in size...
As I recall, RDRT had a separate group working on a different GMR/CMR R&D road map during this time -- the ole buckshot approach to R&D. I think your instincts are right that they may have folded this effort and committed to the CPP-GMR sensor resulting thus far in an impressive demo, but it would be useful to know this for a fact.
I'm also curious if there is anything in the Livermore Labs/RDRT deal that guarantees RDRT exclusivity. My layman's impression is that these taxpayer-funded R&D/industrial deals normally don't have the same kind of exclusivity as, say, patents, which give a party a right to exclude others from using the innovation without permission or compensation for a certain period of time (currently 20 years from date of application).
Thanks again.
Gus
P.S. Re: SEG and RDRT. As you know more than I, RDRT was one of the financial backers of Quinta as well as its primary technical collaborator before SEG bought Quinta. Could the rumors about a long-term SEG/RDRT deal revolve around OAW instead of GMR/CMR head technology? I look at the darwinian way that the economics of the disk drive business are evolving and it seems to me that it is in SEG or Fujitsu's best interest to keep RDRT to nothing more than swing supplier status since RDRT is one of the primary suppliers to its competitors. As just one reference to the way SEG (or any vertically integrated player) could operate, I point you to the SEG/Headway head supply relationship covering Headway's proprietary dual stripe MR head (DSMR) tech wherein SEG is licensed to manufacture 70-75% of its DSMR head requirements (used exclusively for the Cheetah program), but is still contractually obligated to buy 25-30% of its supply requirements from Headway. Thanks for your thoughts. |
