Multilayer plated wire memory system surpasses planar thin film memories because of its high speed, simplicity, and high output. The device consists of 5 mil Be-Cu wire plated with Ni-Fe alloy about 1 micron thick crossed orthogonally by word lines

Kadish, D.

English

NASA Technical Reports Server

Jon magnetic Ni-P 
verlay 0.2 micron 
Permalloy 
=1.0 micron 
Fe-Co 
1.0 micron 
June 1968	 -	 Brief 68-10205 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Multilayer Plated Wire Shows Promise as Memory Device 
Be-Cu Wire with 
Gold Overlay
Advanced memory systems are needed in modern 
computer technology to keep abreast of constant 
improvements being made in electronic, circuitry and 
packaging techniques. The plated wire memory in 
particular appears most attractive because of its high 
output compared to planar thin film memories and 
also because of its high speed and simplicity. 
Basically, the device consists of 5 mil Be-Cu wire 
plated with an 81% Ni-19% Fe alloy about 1 micron 
thick crossed orthogonally by word lines. The dis-
tinguishing feature is the easy axis orientation along 
the circumference of the wire in a closed flux con-
figuration. The resultant low demagnetization value 
in the remanent state permits relatively thick films 
to be used. Since the amplitude of the output is' 
directly proportional to the volume of the material 
and thus to the thickness of the element, a relatively 
thick plated wire device is capable of outputs from 15 
to 50 my in the destructive mode and on the order of 
3 to 10 m y in the nondestructive mode.
Operation of a plated wire device is similar to the 
operation of a single flat film in many respects. Ap-
plication of a word current causes the magnetization 
vector to rotate toward the hard axis with the polarity 
of the outpdt signal identifying the stored bit, and the 
central Be-Cu wire serving as the sense line. The 
closed flux configuration of the plated wire device 
enables its magnetization to be rotated to an angle 
smaller than '90°. Upon termination of the next read 
current, magnetization returns to the original state, 
thus providing a nondestructive readout. 
Writing is by the driving of a small write current of 
appropriate polarity through the Be-Cu wire prior to 
terminating the "read" current, in a manner identical 
to the steering of flat films. Because the plated wire is 
capable of both writing and reading speeds in the 
submicrosecond region, it can be used with equal ease 
in scratch pad or program store applications. 
A multilayer plated wire of crosssection as illu-
strated has been used experimentally with' promising 
(continued overleaf) 
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results. High-coercive force Fe-Co is plated over 
Ni-P preplate. An additional layer of Ni-P is plated 
and a low-coercive force Permalloy is plated over this 
Ni-P. The coercive force of the Fe-Co is designated 
by Hc and the low coercive force of the Permatloy by 
Hi so that H> > H. Bit information is written into 
the Fe-Co layer which acts as a steering mechanism 
for the Permalloy layer switching it into a "I" or "0". 
A low amplitude current pulse is applied, when read-
ing information, which does not switch the Fe-Co 
layer (because of its high-coercive force) but does 
switch the low-coercive force Permalloy. The Permal-
toy is, therefore, always switched in the direction of 
the Fe-Co layer with Co acting as a keeper. 
Notes: 
I. This device appears superior to the conventional 
single layer permalloy-plated wire wherein, while 
operating in the nondestructive mode, the mag-
netization vector, by rotating through an angle 
approaching 900, can destroy the written informa-
tion.
2. Inquiries concerning this experimental investiga-
tion may be directed to: 
Technology Utilization Officer 
Manned Spacecraft Center 
Houston, Texas 77058 
Reference: B68-10205 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546.
Source: Donald Kadish

of Massachusetts Institute of Technology

under contract to

Manned Spacecraft Center 
(MSC-I 1587) 
Brief 68-10205	 Category 01


Multilayer plated wire shows promise as memory device

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