As always, thanks Lee. I think it is fair to say that this 10Q may end up being one of the most misunderstood 10Qs in the 53 year old history of Ampex. There is usually opportunity in that kind of situation so if anybody figures out what it is let me know before the market opens.
Seriously, I think now is an especially good time to go over what we know so far of KM+MR and relate it to the very nuanced pieces of information in this filing.
Two weeks ago, on 4/15/97, Tom Coughlin of Ampex made a presentation before a group of technical folks at the UC-San Diego CMRR. It's useful to review what he said about KM+MR:
exchange2000.com
Recent work with SAL MR heads indicates that the keeper layer can be saturated by the MR element bias field. Keepered media may be able to improve the off-track performance of the MR heads. The unsaturated keeper surrounding the region saturated by the MR element bias field acts as a shield. This shield enhances the existing MR head magnetic shields and in addition shields the MR element from adjacent tracks. We believe that this technology can be extended to all magnetic recording systems to improve usable recording density and product performance.
As you recall, on 11/27/96, Ampex had disclosed that they were able to demonstrate the activation of the keeper layer with a common MR head to a group that included a major disk drive maker and a major head manufacturer.
We now know from the Tom Coughlin abstract that they were able to do so by using the bias scheme inherent in a SAL MR head design without having to use a permanent magnet or a separate wire for the bias current. Below is a link to an IBM description of the biasing scheme of a SAL MR head.
storage.ibm.com
IBM has also developed a unique, patented soft-adjacent layer (SAL) biased MR sensor structure. Electricity passing through the MR sensor creates a magnetic field that interacts with the magnetization of the underlying soft film. This transverse biasing ensures that the magnetic rotation in the MR film occurs at an optimum angle with respect to the sense current, producing the preferred linear-responsive MR signal. To maintain the MR sensor's stability and to suppress magnetic domain noise, a longitudinal bias is also applied by an additional structure, the exchange-bias, or hard-bias, layer.
We also know from the abstract that Ampex is using the KM layer to enhance the shields which are necessary to focus the very sensitive MR sensor. Here is a link to a Seagate paper that describes it better.
seagate.com
An MR read head consists of a read element located in the space between two highly-permeable magnetic shields. The shields help to focus the magnetic energy from the disc and reject stray fields.
Now let's go to the information in the 10Q. Ampex is now saying that
"During the first quarter of 1997, the Company demonstrated under laboratory conditions a significant increase in the capacity
of MR heads utilizing keepered media."
This IS significant. How significant? I am honestly still trying to figure out. You see, there are certain variables possible with AXC's KM technology:
1) thickness of the keeper layer (e.g. 70 nm, 140 nm, etc)
2) size of the bias current (the thicker the keeeper the larger the bias)
3) composition of the keeper layer (sendust, permalloy, etc)
4) position of the keeper layer (underlayer or overlayer)
5) source of bias (ac, dc, permanent magnet)
And probably some more that I am not aware of, but suffice it to say that these variables create combinations that can be used to optimize
KM for a particular head design.
Ampex is now telling us that not only have they been able to activate the keeper layer, but in one particular combination of variables they have been able to demonstrate a"significant increase in capacity." In inductive recording, the KM reduces the spacing loss in inductive heads and produces the extra capacity. What I know is there is minimal or no spacing loss in MR heads. This leads me to the tentative conclusion, open to correction, that they are getting the significant increase in capacity from the improved shielding effects. Again going back to the Tom Coughlin abstract....
"... Keepered media may be able to improve the off-track performance of the MR heads. The unsaturated keeper surrounding the region saturated by the MR element bias field acts as a shield. This shield enhances the existing MR head magnetic shields and in addition shields the MR element from adjacent tracks...."
Not bad work from the people who invented the MR head!
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