A111D3 Dfl^l3M

NATL INST OF STANDARDS & TECH R.I.C.

FOREIGN AND

DOMESTIC

ACCOMPLISHMENTS

IN MAGNETIC

BUBBLE DEVICE

TECHNOLOGY

NBS Special Publication 500-1

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards
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1977 COMPUTER SCIENCE & TECHNOLOGY:

Foreign and Domestic Accomplishments in

Magnetic Bubble Device Technology

Robert B. J. Warnar

Peter J. Calomeris

Institute for Computer Sciences and Technology

National Bureau of Standards

Washington, D.C. 20234

U.S. DEPARTMENT OF COMMERCE, Elliot L. Richardson, Secretary

Edward 0. Vetter, Under Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

U NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued January 1977
Reports on Computer Science and Technology

The National Bureau of Standards has a special responsibility within the Federal

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standards, guidelines, and technical advisory services to improve the effectiveness of

computer utilization in the Federal sector, and to perform appropriate research and

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notices of publications in this series should complete and return the form at the end of

this publication.

National Bureau of Standards Special Publication 500-1

Nat. Bur. Stand. (U.S.), Spec. Publ. 500-1, 50 pages (Jan. 1977) CODEN: XNBSAV

Library of Congress Cataloging in Publication Data

Warner, Robert B. J. Foreign and domestic accomplishments in magnetic bubble device technology.

(Computer science & technology) (National Bureau of Standards

special publication ; 500-1) Bibliography: p. Supt. of Docs, no.: C13. 10:500-1

1. Magnetic memory (Calculating-machines)

2. Magnetic bubble devices. 3. Garnet. 4. Amorphous substances.

I. Calomeris, Peter J., joint author. II. Title. III. Series. IV. Series: United States. National Bureau of Standards. Special publication ; 500-1. QC100.U57 no, 500-1 [TK7895.M3] 602Ms [621,38I9'533] 76-608386

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402

(Order by SD Catalog No. C13. 10:500-1). Stock No. 003-003-01724-8 Price $1.10

(Add 25 percent additional for other than U.S. mailing).
NOTE

Reports on commercial developments included

in this publication were obtained from the

open literature, supplemented in most cases

by site visits and meetings with appropriate

company representatives. No proprietary

information of any kind is included. Opinions

about comparative merits of the developments

were found in the published literature, and were not generated by the authors of this

report. Inclusions or exclusions of specific

developments are strictly reflections of

the published literature. NBS did not

experimentally verify the accuracy of the

statements from the published literature or any of the companies cited. Specific

identifications of companies and developments

in this report cannot be construed as recommendation or endorsement by the

National Bureau of Standards.

iii
PEEFACE

This document assesses the status of magnetic bubble technology as displayed by

foreign research and manufacturing facilities. Japanese and Western European

capabilities and accomplishments in magnetic bubble technology are compared to the

United States position. Both technical and economic factors are addressed and described.

Conclusions suggesting future impacts of magnetic bubble memories on computer technology

are presented.

Information contained in this report was derived from the open technical literature

and from private interviews with various U.S. technical experts. Where possible,

references in the open literature are cited, although the opinion of technical experts were checked in order to substantiate certain points.

The technology assessment resulting in this report was conducted by the Information

Technology Division of the Institute for Computer Sciences and Technology, National

Bureau of Standards, as part of an "Advanced Computer Technology Survey" project.

Mr. Robert B. J. Warnar was the principal technical investigator and was responsible for

the preparation of this report. He was assisted by Mr. Peter J. Calomeris, Mr. Sidney B. Geller of the Computer Engineering Division served as technical consultant. Editorial

assistance was provided by Mr. Edwin J. Istvan, Acting Chief of the Information Technology

Division, and by Mr. George E. Lindamood, Project leader.

iv
CONTENTS Page

Note iii

Preface iv

Abstract 1

1 . Magnetic Bubble Device Overview 1

Magnetic Bubble Technology 1 Magnetic Bubble Device Characteristics 2 Technical Obstacles in Magnetic Bubble Devices 4 Magnetic Bubble Device Applications 4 Memory Application Trends 5 Future Magnetic Bubble Memory Design 7

2 . Magnetic Bubble Parameters 7

Magnetic Bubble Materials 7 Magnetic Bubble Diameters 13

Magnetic Bubble Memory Storage Density 13

Magnetic Bubble Chip-Bit Densities 15

Magnetic Bubble Velocities 15

Magnetic Bubble Data Rate and Access Time 15

Magnetic Bubble Device Power Dissipation 19

Magnetic Bubble Device Prices 19

3. Foreign Magnetic Bubble Technology 19

Magnetic Bubble Technology in Japan 19

Magnetic Bubble Technology in Great Britain 24

Magnetic Domain Technology in France 27 Magnetic Bubble Technology in The Netherlands 28

Magnetic Bubble Technology in the Federal Republic of Germany 29

4. Concl usions i 30

5. Glossary 34

Glossary of Terms Applicable to Magnetic Bubble Technology 34

Glossary of Memory Terms 36

6. References 39

V
LIST OF FIGURES

Page

Figure 1 - The Memory Access Gap 6 Figure 2 - Magnetic Bubble Materials 9, 10, 11 Figure 3 - Diameters of Magnetic Bubbles 12 Figure 4 - Densities of Magnetic Bubbles 14 Figure 5 - Magnetic Bubble Chips 16

Figure 6 - Velocity of Magnetic Bubbles 17 Figure 7 - Data Rate of Magnetic Bubbles 18

Figure 8 - Power Dissipation per Magnetic Bubble 20

Figure 9 - Magnetic Bubble Device Prices 21

LIST OF TABLES

Table 1 - Specifications for a Future Magnetic Bubble Memory Device. . .

'. 8

Table 2 - Magnetic Bubble Technology in Japan 25

Table 3 - Magnetic Bubble Technology Accomplishments in Japan and the

United States 26

Table 4 - Non-U. S. and U.S. Magnetic Domain Devices (1975) 33

vi
FOREIGN AND DOMESTIC ACCOMPLISHMENTS IN MAGNETIC BUBBLE DEVICE TECHNOLOGY

Robert B. J. Warnar

Peter J. Calomeris

ABSTRACT

: This document assesses the status of magnetic bubble technology as displayed by

i non-U. S. research and manufacturing facilities. Non-U. S. research and U.S.

j accomplishments are described while both technical and economic factors are addressed.

I Magnetic bubble devices are discussed whenever their application could impact future

: computer system design. Generally the magnetic bubble device can be applied to a computer

system as a peripheral mass memory. Magnetic bubble devices are produced from either

synthetic garnet or amorphous materials rather than from familiar silicon material. The

i document contains a significant bibliography to support certain main points which are

I supplemented by information supplied by the library of the Information Technology Division

j (ICST-NBS) and from private interviews with various U.S. technical experts.

I Key words: Amorphous materials; bubble; field-access; garnet; guide-pattern;

' magnetoresistance; nonvolatil ity; orthoferrite; photolithography; uniaxial structures.

1. MAGNETIC BUBBLE DEVICE OVERVIEW

Magnetic Bubble Technology

Magnetic bubble devices utilize the mobile properties of cylindrical magnetic

domains. Early this century, spontaneously magnetized crystalline structures (domains)

were found to exist in metals such as iron, cobalt, and nickel. The magnetizations

ll of these domains were randomly aligned in all directions. This randomness is typical

' in polycrystal 1 ine materials. [1]

Early experimenters found thai polycrystal 1 ine magnetic properties were difficult

to control. Ensuing experiments with single crystal magnetic material, which have

I magnetic moments that are aligned with each other (uniaxial structures), demonstrated

I properties which were relatively easy to manage. [2]

Manageability of the magnetic properties within the uniaxial films (usually

consisting of magnetic oxides) is greatly facilitated by the use of a microscope setup

:, which permits visual observation of the magnetic domains by exposing the relatively

f transparent oxides to polarized light. The Faraday effect causes the plane of

'l polarization of the light to rotate, depending on the direction of magnetization of

; the domains located in the oxide film. The microscope setup allows the experimenter

[ to distinguish the magnetic domains with their magnetic moments pointing upward from

I those with their magnetic moments pointing downward. Faraday effect observations reveal

I that magnetic domains within the ferromagnetic oxide films look like randomly oriented

[ worm-like strips when the films are not in a magnetic field. When a magnetic field is

'' applied perpendicularly to the plane of oxide, it causes the magnetic strips to

1 contract and divide into little circular islands initially described as "magnetic soap

I bubbles." These "bubbles" are actually cyl indrical ly shaped domains which extend through

; the entire thickness of the film. The trace of the cylinder top on the surface of the

j film is perceived as a circle under Faraday effect observation. These circles are what

j eventually became known as "magnetic bubbles." [3,4]

1
Although many scientists became active in researching these uniaxial bubble domain

properties, the major breakthrough was made by A. H. Bobeck (Bell Telephone

Laboratories) in 1967. Bobeck introduced the idea that the magnetic bubble must be

magnetized normal to the surface of the oxide in which it is located. Experiments

verified this and Bobeck then showed that it was possible to move the bubbles in any

direction within the plane of the oxide (YFeOs) film by the application of a proper

external magnetic field. [5]

From the time of Bobeck's breakthrough until now, orthoferrites , garnets, and

amorphous materials have been studied for application in magnetic bubble devices.

During the history of material research, (totally different in concept than the

familiar silicon technology approach), dozens of experimental bubble devices using

many types of guide patterns (which are used to provide pathways for bubbles) were

invented by material researchers. [1]

Magnetic Bubble Device Characteristics

Magnetic bubble research and development has been evident for the past ten years.

However, as of today, no standard materials, methods of bubble propagation, chip size

or chip capacity, power supply voltages, etc., are visible among laboratory models.

Furthermore, no commercial devices can be found as yet in the stock of electronic

wholesale houses although several special purpose bubble memory systems have been

delivered such as those by Rockwell International to NASA for use in space

recorders. [6]

According to some expert technology forecasters, if magnetic bubble devices are

to survive, manufacturers must enter their products into the commercial markets as soon

as possible after the device conception and characterization is completed. This is the

tradition in the semiconductor device technology.

The following manufacturers, both U.S. and foreign, are some of the foremost

developers of magnetic domain or bubble materials or devices: [7]

Bell Telephone Laboratories (BTL)

Cambridge Memories (in connection with Crouzet, France)

Hewlett-Packard (HP)

International Business Machines (IBM)

Monsanto

North American Rockwell Electronics (NARE)

Texas Instruments (TI)

Uni vac Crouzet, SA (France)

Plessey Microsystems (England)

Philips Gloeilampen Fabrieken (The Netherlands)

Siemens (Germany)

Fujitsu Laboratories, (Japan) Ltd.

Hitachi (Japan) Ltd.

Kokusai Denshin Denwa Co. (KDD - Japan)

Nippon Electric Co. (NEC - Japan) Ltd.

Nippon Telephone and Telegraph Public Corp. (NTT - Japan)

Tohoku Metals Industries (Japan)

Tokyo Shibaura Electric Company, (Toshiba - Japan) Ltd.
Scientists associated with the above research and manufacturing facilities have

published articles which indicate numerous favorable bubble characteristics. Arthur D. Little, Inc., has accumulated a great deal of information on the various characteristics

of magnetic bubble devices; some of these are: [7]

High function packing density

Nonvolatil ity

Destructive and nondestructive data operation

Bidirectional register operation

Low energy dissipation

Negligible standby power operation

High resistance to shock and vibration

Relative light weight construction

Low volume construction

Storage, switching and logic function operation

Material impurity resistance

Radiation resistance

Synchronous and asynchronous operation

Visible device operation (via special microscope setup)

Potential low cost production

Parallel function operation

High data-storage-density, low power operation, good production yield, non- volatility, and radiation resistance are the outstanding desirable characteristics of

j the magnetic bubble device. Bit-storage-density of a future magnetic bubble memory

^ system could become as high as one billion bits per square centimeter. Generally, it

appears that bubble density is limited primarily by the fabrication techniques in deposition of small guide patterns and detectors rather than the actual size of the

' bubbles. The closest developing, competing technology, charge-coupled devices, will

, have great difficulty in approaching such densities at comparative yields. [8]

Most of the power required to propagate bubbles is dissipated in the elements which

produce the magnetic fields that move the bubbles along their guide pattern paths.

I Experiments show that small bubbles require less propagation power than the larger

I bubbles. Consequently, the smaller the bubble, the greater the density and the less power

I per bubble is required. In addition, some smaller bubbles are capable of moving at higher

velocities. Experimental bubble memories are capable of operating at 10 nanowatts per

' bit; a figure which semiconductors will find hard to compete with.

Despite the attractive bubble device features, several drawbacks deter bubble

I device production: [7]

Temperature sensitivity

Relative poor signal-to-noise ratio

Lack of standard material

Low voltage interface

Serial memory operation

Low speed data rate

Limited production technology

Slow data rate, serial data access, and temperature limitations are the most serious

I of these drawbacks. After ten years of bubble research, most laboratory memory models

I cannot exceed a data rate of one megahertz (1 MHz) under favorable temperature

I conditions. Other memory devices such as crossties, semiconductors, and optical memories

i are expected to be faster than the magnetic bubble memory and are intrinsically less

i' sensitive to temperature.

3
Magnetic bubble materials, such as garnets, require doping by several elements to reduce undesirable characteristics such as temperature sensitivity and low speed operation.

By comparison, silicon usually requires doping by only one element. [9]

Fortunately, bubble device research facilities are able to make use of several

fabrication and production processes which are already established in the silicon

technology. Photo, E-beam, and X-ray lithography and ion implantation techniques can be

applied to bubble hosts. However, the utilization of these existing fabrication techniques

does not guarantee that bubble characteristics are exploited to their fullest extent. If

bubble devices are to realize their fullest potential, fabrication techniques capable of

producing micro-miniature circuits of one to two orders smaller than are presently available

will be necessary. In the meantime, viability of the bubble device could very well depend

on technical acceptance by the electronic market rather than on device performance. [8, 10]

Technical Obstacles in Magnetic Bubble Devices

The most severe obstacle in the development of magnetic bubble devices is the

requirement for the use of relatively new garnet materials rather than the use of welldeveloped silicon materials. [6, 11]

The second obstacle is the reluctance of equipment manufacturers to accept an unproved

memory device.

The third obstacle is the combination of several undesirable technical characteristics

which are inherent to magnetic bubble devices: temperature sensitivity, low speed, and

low-signal-level operation. It is anticipated that the temperature problem will eventually

be solved. The low speed, low-signal -level operation problems of bubbles are considered

the most difficult obstacles by scientists and keep the magnetic bubble memory from

becoming a large, fast random access memory. [7]

To overcome these obstacles, magnetic bubble device manufacturers must offer

compensating device features such as super-high bit-storage-density, ultralow power

operation, and low cost. Currently, such goals have not been attained, and magnetic bubble

devices are therefore not competitive with other more developed technologies such as silicon

devices and some mechanical memories.

It is concluded that magnetic bubble devices will eventual ly gain acceptance as blockoriented, random access memories in computer systems. In this role, magnetic bubble

memories will eventually replace mechanically operated peripheral memories such as disks

and drums. [7, 16]

Magnetic Bubble Device Applications

Foreign literature suggests several applications for the bubble memory. The following

listing suggests how foreign magnetic bubble memory manufacturers plan to apply their

products

:

. Japan - Telephone and television applications. [12]

. England - Mass memory systems aimed at the bank data

capture systems, computer cache memories. [13]

France - Digital television systems, avionic displays,

high performance digital recorders, satellite memories,

and small disk replacement memories. [14]

4
. The Netherlands - Digital recording systems. [15]

. The Federal Republic of Germany - Disk and drum

replacements. [16]

Some potential applications, mentioned in the researched literature, are: [8, 17]

. Portable (including pocket-type) calculators

Intelligent terminals

The integration of magnetic bubble memories into pocket calculators would improve

processing capacity tremendously. Calculators would be able to store large programs,

possibly loaded via telephone lines from distant host computers. (Currently available

programmable hand calculators are programmed only by the insertion of various magnetic,

programmed strips. Each program requires a different strip and the contents of the

calculator memory are lost when the power is turned off.)

The described magnetic bubble memory calculator should incur very little service

computer usage cost since the connection period to the service computer can be short and

infrequent. The increase of cost of the hand calculator can therefore be tolerated since

the increased processing power of the calculator makes the unit capable of meeting many

"costly terminal" requirements. [8, 17]

The features of a future, readily available, and easily adaptable hand calculator are:

. Improved Portability - afforded by the low power operation

of magnetic bubble memories;

. Increased Processing Power - obtained through the use of

both vast bubble memory and silicon microprocessors;

and

. Permanent Program Retention - allowed by the nonvolatil ity

of magnetic bubble memories.

In the case of the intelligent terminals, the use of large magnetic bubble memories

can be extremely cost-effective in the long run. The reduction of operation costs occurs because large programs and data bases can be maintained within the terminal,

The current influx of microprocessors into intelligent terminals will also result in

the demand for more memory. Foreign manufacturers like Hitachi, Philips, Bell Northern

Research of Canada, and Plessey Microsystems are all producing their own microprocessors

or microcomputers.

Memory Application Trends

At present, bubble devices could be implemented in the computer as memories located

between the fast main memory and the external mass memory. Device application in this area is presently competed for by charge-coupled devices, crossties, and other exotic

memories such as potassium nitrate (KNO3) devices.

The "Memory Access Gap" shown in Figure 1, reflects the differences in characteristics

between computer main memory and peripheral mass memory. Some foreign and U. S. manufacturers are seeking to narrow the access gap by substituting magnetic bubble iiass memories in place of peripheral mass memory devices such as disks and drums. Such

substitution may become commercially viable within the next five years since silicon device

mass memories are still rare; slow serial read-out operation is common; and operational

requirements are not terribly stringent. [18]

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Future Magnetic Bubble Memory Design

For market acceptance, magnetic bubble memory manufacturers must further develop their

products to a point at which the advantages of magnetic bubbles over other technologies

are clearly evident. This is presently not the case. The magnetic bubble memory

characteristics that must be further developed are bit-storage-density and memory access

time paired with low cost per memory bit. [6, 19]

According to some technology forecasters, magnetic bubble memories must be able to compensate with higher speeds to offset their higher costs when compared with mechanical

memory technologies to gain acceptance in the marketplace. A factor of ten-to-one in

speed is quoted to offset the current ten-to-one cost differential. [8, 10, 20]

Specifications for a future cost-effective magnetic bubble memory that could find a favorable market are presented in Table 1.

2. MAGNETIC BUBBLE PARAMETERS

Magnetic Bubble Materials

Since the discovery of the magnetic bubble, researchers have been involved in the task

of determining which magnetic material is best suited for use in producing devices. Most

of the materials used for magnetic media contain rare earths. The inclusion of these

elements produces magnetic media with the desirable magnetic properties. [1]

Magnetic bubble materials should be low cost, readily available, and should exhibit

the following characteristics:

a. Stable magnetic axes as a function of temperature,

humidity, etc.

b. Easily workable crystal structures.

As the result of much research, three groups of materials have emerged as candidates

for magnetic media

a. Orthoferrites [21]

b. Garnets [22, 23, 24, 25, 26, 27]

c. Amorphous film material s [28, 29, 30]

Orthoferrites are characterized by the formula A Fe O3, where A can be an element

similar to any of those used in garnets. The general formula for garnets is A3 85 O12,

where A and B are different types of elements with A being a large radius ion such as any of the rare earths and B a smaller radius ion such as any of the transition metals

like iron (Fe). Amorphous films are unlike garnets and orthoferrites since they exhibit

noncrystalline structures. The amorphous films are composed of metals such as cobalt and

certain rare earths like gadolinium (Gd). [29, 31]

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MAGNETIC BUBBLE MATERIALS

10" 10' 10

FILM THICKNESS

(MICROMETERS)

1 10

1969

1970

1971

GdlG(Gd3Feg0^2

Sm (FeO,

Dy (FoO,

Lu (FeO,

Er(FeO,

Eu (FeO

Nd (FeO.

Ho (FeO,

Tb (FeO,

Tm (FeO,

Tb g Tni

g FeOj

Gd (FeO,

Y (FeO.

Yb (FeO,

CIT(CARNEGIEINST. OFTECHN.)

| BTL(BELL TELEPHONE LABORATORIES)

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BTL BTL

BTL

BTL BTL

BTL

BTL

BTL

BTL BTL

BTL

BTL

BTL NiFeCo (CAMBRIDGE RESEARCH LAB)

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3 Tm FeOa

Sm.55 "'b.45 FeOa

CRLUSAF*

BTL

BTL

BTL

Sm^g Tb

,5 Fe03

Otl2.32 Tb ^ Eu 09 FegO,2

BTL

PRL (PHILIPS) 1

•DOMAIN TIP MEMORY

^ THE NETHERLANDS

FIGURE2(a)

9
MAGNETIC BUBBLE MATERIALS

IDFILM THICKNESS

-(MICROMETERS)'

10 1 10

.1

1972

1973

F«75 G<l25

Fegi Gdi9

Fego Gd20

Fe53Gd47

Fees ^'^32

Fe52 Gd48

Fegg Gdi2

Feg4 Gd5

Fe45 Gd54

Fe28 Gd72

Fe43 '''*57

Fei5 '''185

Fe22 Gdyg

Fe34 Gdgg

Eu2.o Yi 0 F85O12

EU3 F85O12

IBM IBM

IBM

IBM

IBM

IBM IBM

IBM

IBM

IBM

IBM

IBM

IBM

IBM

IBM

Sm 4 Y2 6 2 F83.8 O12

IBM

BTL

Gd Fe

Gd Co

IBM IBM

Ni Fe (PROPAGATION STRUCTURES) IBM

Y 2.75 Sm 25 Ga ^^ ^ Fe 3 9 0^2

Eu 6Y2 4 Fe 3 9 Ga ^ ^ 0^2

^•".5^2.5 1.2 F8 3.8 O12

BTL IBM

BTL

FIGURE 2(b)

10
MAGNETIC BUBBLE MATERIALS

10" 10' 10

FILM THICKNESS

(MICROMETERS)

1 10 -1

1974

1975

Ho Co

Ho Ni Ho Fe

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(EU2.0 Yi.o) ''85O12 Gd Co

Y2.5 (^^ 1.2 3.8) O12

GtlO.S Y2.5 Ga Fe40i2

Ni Co

IBM

IBM

IBM

BTL

IBM

IBM

IBM

IBM IBM

ELECTROTECHNICAL LAB.

^

CROUZET

'FRENCH

^JAPANESE

FIGURE 2(c)

11
DIAMETERS OF MAGNETIC BUBBLES

(MICROMETERS)

10' 4-

10' 10 10

-1

132-BIT S.R.( SHIFT REGISTER)

1969

1970

1971

1972 vSHIFT REGISTER BUBBLE DIAMETERvn

^^^^^^.^;^^^x^^^r>^^^^\^^\^^N,^^^:^,^^>^i'^^,>v^ Eu 2.0 ^1 0 ^^5^12 - ^

'

1973

1974

1975

T-BAR PROPAGATION CHANNEL^

TERBIUM ORTHOFERRITE

^"".SS ^''.45 ^"^3 MAGNETOPLUMBITE (Pb Fei20ig)

BELL TELEPHONE LABORATORY (BTL) (D)

BTL(D)

BTL(M)

BTL(M)

BTL(M)

THULIUM OR TERBIUM BUBBLES

Sm.55 Tb.45 FeOa

earLy MAGNETOnESiStiVE SENsOlt 8UB6tE.MEM0RY . . .. . .

BTL(M)

SAMARIUM TERBIUM ORTHOFERRITE

SYNTHETIC GARNET (A3 Fe50i2)

BTL(M) INTERNATIONAL BUSINESS MACHINES (IBM ) (D)

BTL(M)

BTL(M)

Pb Fei20i9 GARNET PERMALLOY DEVICE

BTL(M)

NORTH AMERICAN ROCKWELL

ELECTRONICS (NARE)(D) IBM (D)

Eu 2.0 ^1.0 F85O12

IBM(D)

IBM(M)

MAGNETORESISTIVE BUBBLE MEMORY

GARNET FILM GADOLINIUM COBALT AMORPHOUS FILM

IBM (D) BTL(M)

IBM (M)

20 KILOBITS CHIP BUBBLE MEMORY

BISMUTH-THULIUM GARNET

BTL(D)

RADIO CORPORATION OF AMERICA

(RCA)(M) 100 BITS SHIFT REGISTER [(Eu2 Y-j) Fe50^2l

100 BITS SHIFT REGISTER (GdCo)

IBM (D) IBM (D) AMORPHOUS GdCo Films

^3 """S-X ^"X °12 Eu 10 Yb2.o F95O12

IBM(M)

PHILIPS, HOLLAND

IBM(M)

Gd Co AND Gd Fe (EQUIVALENT BUBBLE SIZE) MOVING DOMAIN: MEMORY .. V MAGNETIC BUBBLE MEMORY

IBM(M)

GADOLINIUM-IRON ALLOY FILM

CROUZET, FRANCE (D) ROCKWELL INTERNATIONAL (Rl) (D) KOKUSAI DENSHIN DENWA,

JAPAN (KDD) (M)

= EXISTING MATERIALS (M) EXISTING DEVICES (D) = POTENTIAL

FIGURES

12
Figures 2a, b, and c provide a historical overview of some materials used since iy6y.

The material is identified by its formula, its research facility, its thickness, and the

year in which the article containing the information was published. The Figures 2(a), (b),

and (c) show garnets in 1971 (Gd2,32 Tb 59 Eu^gg ^65 0i2)> in 1972 (EU3 ¥e^ O12) and in 1974 (Sm^5 Y2 5 Gai_2 ^^3.8 O12).' In T969 we find an orthoferrite in the form of

Tb^5 Tm^5 Fe O3 and in 1971 another by the formula Sm_55 Tb_i+5 Fe O3. Amorphous films

such as'Gd Co and Gd Fe were produced in 1972 through"1974 and generally exhibited better

magnetic bubble device properties than orthoferrites . [32]

Facilities in France are experimenting with nickel -cobalt films in their moving domain

memories (MOD) whose material formula is shown as Ni Co for the year 1975. Other companies

are producing magnetic bubble chips from the garnet formula Gdg 5 Y2^5 Ga Fet^ 0i2» which

is shown in the Figure 2(c) graph for the year 1974. [9, 14, 33]

As a whole, it appears that garnets are used more now than other materials by various

research facilities even though amorphous films appear to have greater potential in bubble

density.

Magnetic Bubble Diameters

As previously mentioned, magnetic bubbles behave like magnetic domain cylinders.

Experiments indicate that the smallest diameter of a cylinder with acceptable stability is

obtained when it approaches the dimension of the film thickness. Thus, if bubbles,

supported by small bubble guides, are very small and the magnetic film is very thin, the

amount of data which is stored per given area can be high. Therefore, not only bubble

device properties but also the fabrication techniques of the materials determine the

storage densities. [2]

Figures 2 and 3 indicate some of the relationships between film thickness and bubble

diameter. Figure 3 summarizes the range of bubble diameters for various materials and

presents a history of technological developments from 1969 to the present time (1975).

Currently, the bubble diameter seems to be somewhere in the vicinity of lO'^^cm or

1 micrometer while the film thickness is slightly less.

The diameter of the domain can be made to vary from that of a strip domain to a magnetic bubble cylinder with a diameter of less than 1 micrometer by increasing the

perpendicular magnetic field. If the magnetic field is increased to a critical value which

depends upon magnetic characteristics of the bubble host material, the bubble collapses.

A "safe" value for a stable bubble is one which is about twice the diameter of the magnetic

bubble before collapsing. [21, 32]

Amorphous films have been produced with bubble diameters smaller (0.1 micrometer) than

garnets. According to the graph. Philips and some U.S. companies have achieved some of the

smallest bubble diameters in garnets (0.5 micrometers). [27, 34]

Magnetic Bubble Memory Storage Density

A superior characteristic of magnetic bubbles over alternative memory technologies is

their potentially high information -storage-density. Experts predict that bubble density

will surpass 10^^ bits per square centimeter (as compared to 10^ bits for semiconductors).

The primary limitation of bubble density is the fabrication process. The limits of photo,

E-beam, and X-ray lithographic processes have been under constant study while the latest

magnetic bubble research breakthroughs have occurred by the use of ion implantation

processes. [8]

Figure 4 provides a historical overview of how magnetic bubble density has progressed

through the years from 1969 to the present. Initially, bubble materials had densities of

10^ to 10^ bubbles per square centimeter in orthoferrites. Predictions for other prospective

materials were as high as 10^ bubbles, or bits, per square centimeter. [7]

13
10^

DENSITIES OF MAGNETIC BUBBLES

(BITS/CM^)

10* 10

5

10 103

-I10° 10' 10' 10' 10^

1969

1970

1971

YbFeOj BTL(M)

Sm-55 Tb

,5 FeOj BTL(D)

ORTHOFERRITE (EXPERIMENTAL) BTL(M)

OTHER PROSPECTIVE MATERIALS.s GARNET

SAMARIUM TERBIUM ORTHOFERRITE

A3 FBj O12 (SYNTHETIC GARNET)

BTL(M)

BTL(M)

BTL(M)

BTL(M)

BTL(D)

BTL(M)

1972 MAGNETOPLUMBITE IBM (M) COBALT FOIL

20 KILOBIT MEMORY DEVICE BTL(D

1973 MAGNETORESISTIVESENSOR MEMORY CHIP. IBM (D)

1024 BITS BUBBLE MEMORY CHIP IBM (D)

; 20 KILOBIT CHIP BTL (D)

IBlvi ^M)

1000 BITS CHIP IBM (0)

100 BITS SHIFT REGISTER (GdCo)

1974 100 BITS T-BAR REGISTER (EU20 Y10 Fe5 0i2 EXPERIMENTAL MEMORY CHIPS (REPORTED

^^J^\ ^v\' ^^^''

l:

' ^^^^v^r';\^ \^^v^x^: '^'^v\.v.%^<. ^

' v^lON-IMPLANTED DISK BUBBLE MEMORY

,^,^VV,)lX\^.V^,^J\^l>l»S^^,^A^a%0^^^^^^v'>k^>>'>^

^^ SFUTURE FILE APPLICATION CHIPXS; N >'iift'i^''»^»'A>V.VAN">.'><>'''i>'.>'Ni'' *> 'i ">^ ^^,v^ vv\

1990 = MATERIAL (M) = DEVICE (D)

FRENCH

JAPANESE

= SYSTEM (S) = POTENTIAL

FIGURE 4
In 1970, 1971, and 1972, garnet materials were developed which exhibited equal or better magnetic and physical properties than orthoferrites. The average density for both

materials is now somewhere between 10^ and lO'' bits per square centimeter. One research

facility reported densities of 10^ bits per square centimeter in cobalt foil materials in 1972.

It must be noted that high bit-storage-densities in materials have not always enabled

the production of high bit density devices (such as memories). The additional area required by bubble guides and detectors almost always drastically reduce chip-bit densities.

Magnetic Bubble Chip-Bit Densities

Figure 5 shows magnetic bubble laboratory devices that have been produced by various

manufacturers. The chip-bit densities are indicated for each device progressively from

1969 to the present, (1975). [35, 36]

Magnetic Bubble Velocities

Figure 6 indicates how fast bubbles move through materials. The speed of the bubble

is usually a compromise between low material coercivity and high bubble stability. As shown in the Figure, bubble speed has increased steadily, but not drastically, from 1970 to 1975. Some of this increase in speed has been achieved through the use of improved magnetic

bubble materials. In general, garnets can have higher bubble speeds than either ferrites

or orthoferrites. [15, 37]

Magnetic Bubble Data Rate and Access Time

The data rate of magnetic bubbles is measured in bits per second and relates to the rate at which data propagates through either the material or device, as presented in Figure

7. This Figure shows the trend of increasing speed of data propagation from 1969 to present

.

The data presented in this Figure also suggest that research facilities first develop

high data rate materials and then try to develop independent devices. [38]

Access time is related to data rate since bubble memories are serial devices. For example, the average access time for a 2048-bit serial bubble memory operating at a 500 KHz clock rate is determined by the following formula:

T-access (average) _ 1 Number of bubbles per device

(Bubble Propagation Rate) ^ 2

=

/R in^- hitc/c..^ X 2048 Bubbles

^ ^048 microseconds

(5 X 10^ bits/sec) 2

The worst access time occurs when the required data have just left the detector and must travel the entire register again. The worst access time is twice the average access

time. Obviously, the best access time occurs when the data are just about to arrive at the

detector, i.e. , one clock cycle avjay from the detector.

Since bubble memories are characteristically serially oriented, bubble devices will

usually be comprised of several optimum length registers in one chip. In this approach,

storage capacity can be great and the access time will be only slightly greater than the access time of one single register. The slight increase in time results from the additional

time needed to choose which register is being addressed. [39, 40]

15
MAGNETIC BUBBLE CHIPS

fBITS/CM^)

10 10^ 10^ 10' 10* 10* 10* 10^ H h

10'

1969

1970

1971

1973

1974

1975

32-BITS SHIFT REGISTER CHIP V BTL

DOMAIN TIP (DOT) SHIFT REGISTER. 1024 BITS : :: CAMBRIDGE RESEARCH OF U.S.A.F.

20 KILOBIT CHIP

20 KILOBIT CHIP

1024 BITS BUBBLE MEMORY CHIP

16,664 BIT CHIP

100 BITS SHIFT REGISTER CHIP

17 KILOBIT CHIP

BTL

BTL

IBM

BTL

IBM

64 KILOBIT CHIP HITACHI

HITACHI

JAPANESE

•DOMAINTIPMEMORY

FIGURES

16
VELOCITY OF MAGNETIC BUBBLES

(CM/SEC)

10 10' 10^ -+-

10' 10

HEXAGONAL FERRITES BTL(M)

1970 GARNET BTL(M)

ORTHOFERRITES BTL(M)

1973 Sm ^ Y2.6 Gai 2 FSgg 0^^ BTL(M)

Y2.75 25 Gai 1 Fe 3 9 0,2 BTL(M)

1974

1975

0 BS E R VEi) M/IVG N ETI C B U B B LE PRO PAGATI ON

YTTRIUM IRON GARNET

IBM(D)

PKILIPS(M)

= MATERIAL (M) = DEVICE (D)

1 THE NETHERLANDS

FIGURES

17
DATA RATE OF MAGNETIC BUBBLES

(HERTZ)

= EXISTING MATERIAL (M)

'DOMAIN-TIP PROPAGATION

SHIFT REGISTERS

= EXISTING DEVICE (D) "CLOCK RATES

= POTENTIAL

FIGURE?

18
I The data rate of the bubble, or its propagation speed, has not improved as fast as one

1^ would expect. Many sources indicate that the average data propagation rate for present

\ devices is about 10^ Hertz. If there is to be a marked increase in this data rate,

materials with extremely low coercivity and high stability will have to be developed.

Unless semiconductor device speed can be attained, long bubble access time may preclude

the use of magnetic bubble devices for main computer memories. [8]

j Magnetic Bubble Device Power Dissipation

I Magnetic bubble devices operate at very low power levels. For example, it is estimated

that a bubble bit dissipates several hundred times less power than even the smallest

] transistor. Figure 8 gives power dissipation data on four examples of bubble memories and

indicates that the average power a bubble dissipates ( i.e. , the energy used to form and

control a bubble) is approximately one microwatt. According to one source, the power to perform 10^^ binary operations a second in magnetic bubble devices would be only 0.04 watt

as compared to 10 watts needed by semiconductor switches. [41]

Magnetic Bubble Device Prices

I Figure 9 graphs the price trends of magnetic bubble devices and systems. For devices

I produced in 1972 through 1974, the projected average price was about 0.025 cents per bit.

Predictions have been made that future bubble memory systems (including total interface

capabilities) could be priced for as little as 0,029 to 0.075 cents per bit. [7, 11]

3. FOREIGN MAGNETIC BUBBLE TECHNOLOGY

Magnetic Bubble Technology in Japan

Although Japanese companies have been studying the magnetic bubble developments for a long time, they did not become heavily involved in this field until the early 1970's.

During this period, less-promising orthoferrite magnetic bubble materials were bypassed in favor of garnet films.

The Japanese government is now actively supporting and subsidizing magnetic bubble

research. Acting primarily through the Ministry of International Trade and Industry

(MITI), a program has been instituted which addresses the following facets of the magnetic

bubble technology: [42]

(a) Material

s

: Garnets and (more recently) the non-crystalline

alloys are being investigated. [26, 43, 44]

(b) Bubble guides : Ion implantation and permalloy research is being performed. [33]

(c) Bubble detectors : Efficient Hall effect and magnetoresisti ve bubble detectors have been developed. [33]

(d) Bubble density : The latest materials are being studied which

is resulting in the production of high bit density bubble memory

chips. [45]

(e) Packaging techniques : Unique packaging techniques which allow

the mass production of bubble devices have been developed.

19
POWER DISSIPATION PER MAGNETIC BUBBLE

(WATTS/BIT)

10"^ 10-2

1969

1970

1971

1972

ORTHOFERRITE MAGNETIC BUBBLE MATERIALS

ORTHOFERRITE V

REPERTORY MEMORY BTL(D)

,\GARNET BUBBLE MEMORY;^

^MAGNETIC BUBBLE DEVICElvs

BTL(M)

IBM(D)

BTL(M)

= PREDICTED DISSIPATION

= EXISTING DISSIPATION

FIGURES

33
MAGNETIC BUBBLE DEVICE PRICES

(CENTS/BIT)

10" 10

-2

1972

1974

M5 X 10!^BITS^MEMORY>^^^^

.xK<S

M X lO^^BITS MEMORY^

M X lOl^BITS MEMORYvxN^

1975

1977

1978

10" H

IBM (D)

IBM(D)

^35 KILOBIT

SHIFT REGISTER CROUZET^ (D)

16 KILOBIT GARNET MEMORY PLESSEY MICROSYSTEMS ^ (D)

Ibits".^^ ARTHUR D. LITTLE INC. (S)

s2x105aBITS-^

1^2 X lO^o^ BITS

N

ARTHUR D. LITTLE INC. (S)

s31 ARTHUR D. LITTLE INC. (S)

ARTHUR D. LITTLE INC. (S)

ARTHUR D. LITTLE INC. (S)

IBM(D)

= EXISTING DEVICE (D) = EXISTING SYSTEM (S)

POTENTIAL FRENCH (COST)

2 BRITISH

FIGURE 9

ZL
(f) Mass production techniques : Unique automatic methods have

been perfected which allow mass inspection for flaws in garnet

fi 1 ms

.

(g) Appl i cations : Many application studies in Japan indicate an intent to introduce bubble memories as replacements for the

fast computer auxiliary memories such as disks or drums and

memories for small office machines. [12, 45]

The following Japanese research and manufacturing facilities are involved in efforts

which collectively provide a complete design structure for the Japanese approach to the

magnetic bubble device technology:

. Hitachi Ltd.

. Kokusai Denshin Denwa Co. (KDD)

Electrotechnical Laboratory

. Nippon Electric Co., Ltd. (NEC)

. Nippon Telegraph and Telephone Public Corp. (NTT)

. Tohoku Metals Industries

Fujitsu Laboratories, Ltd.

Each of these facilities is involved in a particular phase of the magnetic bubble

technology; one researches garnets and another non-crystal alloys, while others concentrate

on applications, packaging, and mass production techniques. [24, 26, 33, 42, 43, 46]

Garnet material research has been conducted at the laboratories of Hitachi since 1971,

The Faraday rotation effect of the bismuth (Bi) substituted rare earth garnets was studied

in great detail by Hitachi. Various material samples were measured for Faraday rotation

and optical absorption. The experiments were successful and material samples (such as Gd2_o Bi 1 0 ^^65 O12) with low optical absorption characteristics and good Faraday rotational

characteristics (up to 80 degrees of rotation) were identified. In research done by

Hitachi, lead (Pb) was added to the iron garnet in order to improve the Faraday rotation

effects. Results indicated that Pb-substituted garnets (Y2^5 Pbo,5 Fet^ 5 Gsq^s 0^2)

produced only half of the Faraday rotational increase that the Bi -substituted'garnet

material had shown. All samples were prepared by the Japanese Central Research Laboratory

(Hitachi). [26, 43]

Other experiments, aimed at the understanding of motion and control of the top velocity

limits of magnetic bubbles, were conducted at the Nippon Telegraph and Telephone (NTT)

Corporation and the Nippon Electric Company (NEC) respectively. The NTT approach used the

deposited conductor techniques to produce bubble motion. The results of the experiments

were not fully understood because "the observed bubble motion is not sufficiently

explained by an existing theory on bubble dynamics," [46]

22
NEC made attempts to improve the magnetic bubble velocity. (Previously, the reported

velocity of their magnetic bubbles resulted in memory data rates of about 1 MHz maximum.)

\j NEC (as reported in 1973) showed an impressive 2200 centimeter/second Oersted velocity

figure for a garnet material which included gallium substitution (Y2^e Eug 2 1 Ga^ 3 Oi2)- This reported velocity is about half of what was reported in the U.S. during the

same period and approximately 1/20 the value reported by Philips (Netherlands) in 1975. [24]

Advanced research with Gdg 5 '^i.'b Fe^ O12 garnets was performed by the

Electrotechnical Laboratory in 1973 according to the Proceedings of the 5th Conference on Solid State Devices. The effort appeared successful in that "hard bubbles" were suppressed by the use of the advanced ion implantation methods. ("Hard bubbles" usually are undesirable bubbles since they tend to propagate more slowly and behave more erratically

than "normal bubbles".) Additionally, this facility produced a Hall effect bubble detector

capable of sensing bubbles and producing a signal output of 0.5 millivolt with a good 30 db

signal-to-noise ratio. [9, 33]

Hitachi, as reported in the Conference proceedings, also overcame the "hard bubble"

problem. In their approach, permalloy was deposited on garnet films. Hitachi found that

the strong exchange coupling between the permalloy and garnet caused "hard bubble"

suppression. Additional efforts in bubble detection were successfully accomplished through

the use of both the Hall effect and magnetoresi sti ve detectors. [47]

With garnets established as bubble hosts, permalloy and ion implantation as bubble

"purifiers," and detectors providing the required signal levels, additional Japanese

facilities were involved in the bubble device technology. Nippon Electric Co. (NEC) and

Tohoku Metals were reported to be working on 2.4 kilobit garnet memory chips according to Electronic News , July 29, 1974. The government project called for application of these

units in a mass filing system (peripheral memory) and a "fast auxiliary memory" system for

internal computer memory use. Other reports indicate similar trends for magnetic bubble

memory applications. Japanese government specifications require a fast auxiliary memory

with a capacity of 10 megabits at access times of 0.1 milliseconds. These specifications

also call for a bubble memory capacity of at least 0.25 million bits per chip by 1978. The

specific application of the total computer system appears to be in "pattern information

processing." [42]

Fujitsu Laboratories, Ltd., is actively involved in developing mass production

techniques for magnetic bubble memories. The facility is addressing both mass production

automatic quality control and device packaging techniques. A television system is utilized

in the quality control phase during which garnet films are automatically scanned for flaws

and defects. Special packaging methods developed by Fujitsu allow for the mass production

of flat package devices with less heat dissipation problems than conventional magnetic

bubble packages.

Kokusai Denshin Denwa Co. (KDD), is currently experimenting with non-crystalline alloys

which could eventually support bubbles with densities two orders of magnitude greater than

the garnets. According to the article, magnetic domains of "spark-like" formation (unlike

the magnetic bubble cylinder) were found with diameters of 1 micrometer (or about five to

ten times greater than the "conventional device" bubble diameter). It is interesting to notice that, even though the alloy bubble is 1 micrometer in diameter, the reported bubble

density is approximated at only 10^ bits per square centimeter. Theoretically, the density

should be much higher than the reported value. It appears that magnetic bubble manufacturers

generally incur fabrication difficulties which result in a relatively high loss in bitstorage-capacities. [44]

No information has appeared on possible applications exploiting the reported

capabilities of the alloy material. The ability of the alloy device to operate as a memory

with associated logic functions in addition to exhibiting thermal writing characteristics

23
may warrant the introduction of a non-crystalline alloy device in a variety of applications

other than pure memory. The ability for thermal writing, for example, may make it possible

to record a film with the use of a camera flash. If this method is successful, magnetic

bubble image sensing could compete with the charge-coupled image devices. [44]

Table 2 indicates noteworthy magnetic bubble research facilities in Japan, their

responsibilities, and goals. As indicated, mass production of magnetic bubble memories

by Japanese companies can be expected in the near future. The recent announcement by

Hitachi of their 64 kilobit memory chip is a strong indication of the present capability

in Japan. The formal announcement to be given within the near future will claim that the

Japanese device is "among the best in the world". [45]

Development of the 64 kilobit device was funded by the Ministry of International Trade

and Industry (MITI). The Hitachi chip, which is to be integrated into the "Pattern

Information Processing System," displays outstanding bubble device characteristics. The

chip contains 5 micrometer bubbles and measures about 6x6 millimeters. Bit density of

the chip approaches 10^ bits per square centimeter. No information is available from which

to estimate the speed of the device, but the Japanese 64 kilobit magnetic bubble chip is

claimed to be the best magnetic bubble device available. [45]

A 32 kilobit Hitachi device is slated to be implemented in office machines (terminals,

document reproduction machines, calculators, and memory typewriters are likely candidates),

point-of-sale machines (cash registers, credit checkers, etc), and character displays by

Spring of 1976 . The magnetic bubble memories are commercial outgrowths of units originally

delivered to NTT. The bit price is estimated at about 0.15 cent for initial systems. The

bubble replacement memory system is said by Hitachi to be only 5 percent of the size of the

replaced drum memory; to weigh only 10 percent as much; and to consume only about one third

as much power. In addition, of course, the magnetic bubble memory has no moving parts. [12]

Table 3 provides an overview of how accomplishments in Japan compare with the present stateof-the-art of magnetic bubble technology in the United States.

Magnetic Bubble Technology in Great Britain

After Crouzet of France, Plessey Microsystems (UK.) was the second corporation found

to advertise commercial magnetic domain memories. Plessey, however, was the first producer

to announce commercial magnetic bubble products.

Previously, little information on the progress of bubble memories in Great Britain

had appeared in the literature.

Some bubble memory designs offered by Plessey should be completely developed by the

middle or end of 1976. At this time, it is said that an 8 kilobit and 16 kilobit magnetic

bubble shift register will be available. [13]

The Plessey magnetic bubble memories appear to be relatively slow (100 KHz data rate).

This results in slow (40 millisecond) data access times when compared to conventional disk

and drum memories which already display 15 millisecond access times. Reportedly, Plessey

officials are aware of this problem and plan to produce a 4 millisecond, 16 kilobit unit

before the end of 1976. A 64 kilobit unit is also under development. [13]

24
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26
Plessey's magnetic bubble memories are all fabricated from garnet material that have

been researched since 1972. The substrates are single-crystal gadolinium gallium garnets

coated with samarium-doped yttrium iron garnet. A significant factor is that Plessey

is offering their products in dual-in-line (DIP) packages. The DIP approach, used for at least ten years in current integrated circuitry components, allows for easy integration of

bubble memories in present day designs. [22, 48]

According to an article in Electronics , Plessey's magnetic bubble memories are aimed

at a bank data-capture system at an advertised price of 0.1 to 0.01 cent per bit. The

replacement magnetic bubble memory systems will probably make use of major and minor

loop architectures--the design mentions "transfer gates"--to achieve the desired

4 millisecond access time. Such efforts require state-of-the-art knowledge of magnetic

bubble behavior and materials. [13, 36]

The 4 millisecond access times of the proposed Plessey devices still do not meet

the 1.5 millisecond access time used by some technology forecasters as a criteria for

disk and drum replacements. Therefore, the commercial venture of Plessey into the

magnetic bubble memory market with the advertised access times could entail great financial

risks.

Magnetic Domain Technology in France

Crouzet (SA) of France, is presently producing moving domain memory cards at a cost

of about 0.2 cent per bit. These moving domain (MOD) memories are similar to the

conventional magnetic bubble memories; however, they are nonvolatile and need no external

magnetic bias fields to form and hold the domains as do magnetic bubble memories. In addition, MOD memories can be fabricated by using conventional thin-film microcircuit

techniques. The drawback of slower data rate times and lower bit densities cause MOD

memories to be generally considered inferior over magnetic bubble memories. [49]

Crouzet has produced a 2 megabit image-refresh memory. The refresh memory system

will be integrated into a military digital television system. Other systems to be

delivered include an avionics display refresh memory and a prototype for a satellite

memory. The latter systems exploit the magnetic domain memory advantages of low volume,

light weight, and low power operation. In addition, since MOD memories are solid-state

devices, the lack of mechanical maintenance results in extremely low failure rates. [14]

The MOD memories in France are not fabricated on exotic substrates. Nickel-cobalt

is deposited on glass substrates which measure 63 millimeters by 54 millimeters at

0.5 millimeter thickness. Each chip has a 35,000 bit capacity with an average access time

of 6 milliseconds. A future line of improved MOD's will have access times of 0.3

mil 1 i seconds

.

Crouzet will be aiming at the small disk market with a high performance MOD memory

replacement. Large disk replacement by MOD memories is not likely to occur since the

low domain bit density of the solid state memory results in either a high cost or a noncompetitive access time machine. [14]

27
MOD memories can be classified as an intermediate technology which exists between

the semiconductor and magnetic bubble memories. Crouzet officials predict that their

product will be less costly than charge-coupled devices, but charge-coupled devices operate

several orders faster than MOD memories. On the other hand, Crouzet feels that their

product competes well with 6 micrometer magnetic bubbles, although magnetic bubble bit

density should be at least one or two orders better than MOD memories. [14]

The significant fact, however, is that the French company intends to produce magnetic

domain memories commercial ly . The production cycle of the MOD memories will undoubtedly

provide the French with valuable magnetic domain memory manufacturing knowledge. If the

MOD memory is an intermediate step toward state-of-the-art magnetic domain memories, the

French firm could produce solid state magnetic domain memories for replacement of current

TV refresh memory, disk, and drum systems.

Magnetic Bubble Technology in The Netherlands

Unlike the mul ti -corporation program in Japan, the effort in Holland with magnetic

bubbles is pursued through just one facility. Philips. Advanced magnetic bubble research

by Philips was first reported in the open literature in the last half of 1971 and deals

with unusual magnetic bubbles called "hollow cylindrical domains."

The unusual "hollow cylindrical domains" discovered by Philips differ from the

conventional solid bubble domains. Hollow cylindrical domains have center regions

whose magnetization is opposite to the rest of the bubble wall while typical solid

bubbles exhibit the same magnetization throughout their entire cylinders. [50]

The "hollow bubble" is found in an orthoferrite called LuFe03 and the description

of the hollow domain bubble is found only in the Philips literature. Examination of

the hollow bubble structure indicates that these domains could exist in several stable

sizes. (Six incremental states were observed which ranged from 400 to 1,000 micrometers

in diameter.) The increase and decrease in size (called "rentation") of the hollow

bubbles is fully controllable by varying the amplitude of the magnetic bias field.

The implementation of the hollow bubble in a solid state bubble processor could

give rise to processing languages other than binary, since the hollow bubble can exist in at least six stable states rather than the conventional two binary states of

present processor logic elements. However, up to the present time, no implementation or

use of the hollow-bubble phenomenon has been described. [50]

The described results of the Philips' experiments display a considerable knowledge

of orthoferrite materials. While most advanced magnetic bubble research facilities are concerning themselves with garnet structures, articles by Philips authors stress the

fact that the low magnetic moment and high crystal anisotropy of orthoferrites makes

this material attractive for magnetic bubble domain material. This material has been

found by most researchers to be inferior to the garnets and is not in general use.

Philips suggests the following applications of materials: [27. 34]

Spinels - recording heads and microwave devices

Hexagonal Ferrites - bubble domain devices ( 2 micrometer

bubbl es

)

28
Orthoferrites - bubble domain devices ( 50-100 micrometer

bubbl es

)

. Garnets - bubble domain devices ( 0.5-10 micrometer bubbles ), microwave devices, and magneto-optic devices.

The following is a Philips listing of crystal -growth processes and some of their

drawbacks: [27, 34]

Sputtering Techniques - produces poor quality for sinqle

crystal material

. Hydrothermal Epitaxy - requires complicated setups

. Chemical Vapour Deposition (CVD)- requires critical control

of various gas streams

Chemical Solution - requires long periods of time for

processing

Liquid Phase Epitaxy (LPE) - exhibits material mixing problems

Philips also suggests that the CVD process has probably better potentiality than

other techniques. The LPE process, according to Philips, is currentl^' the most commonly

used procedure. Some literature from other sources indicates that the LPE process is

commonly used since this procedure requires low equipment costs, produces a high yield, and

adapts easily to variations in garnet compositions. [34]

Philips deposits layers of garnet with a thickness on the order of 1 to 10 micrometers

for use in magneto-optical studies, for applications of magnetic bubbles, and for

integrated single crystal optics. The substrates used by Philips measure 20 millimeters

in diameter and are 0.5 millimeter thick. (Magnetic garnet film is about 1 to 10

micrometer thick.) After the substrates are polished, they are cleaned by Syton, a product bought from the U.S. Monsanto Corporation. The finished products are further

scanned for defects by a scanning electron microscope (SEM). [26, 27]

Despite all of the displayed magnetic domain material knowledge by Philips, no reports have been found which indicate that magnetic bubble products (commercial or military) have been produced and delivered to any customers by this company. It appears

that Philips has made a preliminary choice between the production of magnetic bubble devices

and charge-transfer devices. The decision appears to have been made in favour of

charge-transfer (CT) devices (bucket-brigade and charge-coupled devices) since commercial

CT products are presently available from Philips.

Magnetic Bubble Technology in the Federal Republic of Germany

A survey of German literature disclosed very few sources of information relative to magnetic bubble memories. Siemens has sponsored the writing of several articles for

technical magazines, and these articles indicate that German-made magnetic bubble

prototypes are manufactured primarily from garnet materials Published photographs show

garnet strip domains, magnetic bubbles, and bubble guide patterns. Magnetic bubble

diameters are said to be optimized since gallium is added to the garnet material. A film

of ^2^6 Smg 1+ Gai^2 ^^3,8 O12 "is deposited on a gadolinium garnet substrate. This formula

is identical to tfiat used by Bell Telephone Laboratories. [51]

29
The German-manufactured magnetic bubble materials host 5 micrometer bubbles, while

most advanced magnetic bubble device manufacturers, such as Dutch and U.S. facilities,

are capable of producing bubbles measuring less than 2 micrometers in diameter. [16]

Magnetic Bubble guides, which are deposited on garnet structures, form bubble guide

paths. The guides are made of permalloy material. X X structures, as opposed to T-bar

structures, were .used as bubble guides. Such structures are rarely used in current

magnetic bubble devices made in other countries.

Magnetic bubble memory data rates for the garnet devices made in Germany appear to

be in the 100 KHz to 1 MHz range. Magnetic bubble detectors appear to produce far

greater output signal levels than do the competitive devices. Detector output signal

levels of 50 millivolts were achieved. Output levels of this magnitude are at least

one order higher than values reported by researchers in other countries. It appears that

most manufacturers have found that high-level output detectors suffer from instability.

The high sensitivity of the detectors is difficult to explain, especially since

the associated data rates are not slow. In the past, manufacturers have increased

detector output levels by stretching the initial bubble into large domain strips and

then sensing the increased magnetic energy contained in the large domains. Unfortunately,

the stretching technique could be somewhat time consuming since the incremental increases

of bubble size demands additional operating time. The end result of this stretching

process is usually a delayed output of data. .

Based upon a sketch of a magnetic bubble memory appearing in an article in Electronik , it appears that no unique approaches to magnetic bubble memory architecture are being ' employed. In a table which compared several parameters of magnetic bubble disks,

charge-coupled devices, and domain tip (DOT) memories, most parameters given were similar

to parameters published by non-German sources. However, the magnetic bubble bit density i was given at 0.5 to 2.5 kilobits per square millimeter. It is estimated that the bit | density should be at least ten times higher if 6 micrometer bubbles exist in the garnet ; films. The low packing density of the devices indicates a possible manufacturing problem

which has not been solved. [16]

Several German firms--no names were given--are reported to be building magnetic

bubble prototypes. Magnetic drum and disk replacement is the design goal. !

Magnetic bubble memory research is subsidized by the West German government. It appears that several research facilities are heavily involved in producing prototypes on government contracts. However, the open literature contains little information of how

the involved facilities are progressing.

f.

I 4. CONCLUSIONS i

\ Information found in both non-U. S. and U.S. literature indicates that much of

magnetic bubble LSI circuits are currently produced from garnet materials rather than

from silicon. Silicon semiconductors are most often used in the manufacturing of p contemporary LSI circuitry,

30
Early magnetic bubble devices used orthoferrites initially as media for bubbles,

but it is generally reported that these materials exhibit inferior memory characteristics

when compared to garnet devices. Therefore, orthoferrites have been dropped by many

of the advanced magnetic bubble device researchers. Available information reveals that

virtually all major researchers and manufacturers of bubble devices in Japan, Great

Britain, The Netherlands, the Federal Republic of Germany, and the United States use nonmagnetic garnet substrates and magnetic garnet films for their bubble devices.

Reportedly, amorphous materials are relative new-comers on the scene of magnetic

bubble materials. In many instances, these materials are said to support smaller bubbles

with potentially higher operating speeds than bubbles of the current garnet technology.

Garnets, however, have already been widely accepted as a result of intensive material

research that has been reported for over five years.

Officials of the French company Crouzet announced that nickel -cobal t is the material

used in their domain memory devices. According to the announcement, these memories are called moving domain memories (MOD). These MOD memories are said to present advantages

over contemporary bubble memories in that less exotic substrate materials (glass) and

readily available magnetic films (nickel -cobalt) can be used. In addition, nonvolatility

of the stored MOD information is said to be assured without the use of permanent magnets

that are necessary for magnetic bubble device data retentivity. However, the advertised

access times and bit-storage-densities do not measure up to those of garnet device

parameters although the MOD memories are potentially less expensive to produce.

Technical information published by magnetic bubble researchers stress the importance

of high data-storage-density and fast data access times as goals for their devices. In addition, bubble researchers claim that the nonvolatility and low-power consumption of

the magnetic bubble device packages make this product ideal for portable, battery operated,

computing apparatus.

At present, the bit-storage-capacity of a single magnetic bubble garnet chip has

reached about 64,000 bits; although manufacturers in the U.S. are capable of producing

garnet LSI chips of this density, manufacturers in Japan (Hitachi, etc.) are credited

with the first delivery of a production lot of such devices. Bit-storage-density is said

to be directly related to bubble diameter. Generally, the smaller the bubble, the higher

the bit-storage-density. The garnet bubble chips, produced in Japan, exhibit a 2.7

millisecond access time while potential products in the U.S. are reported to border the

1 millisecond range. Further progress is indicated by predictions that magnetic bubble

memories can surpass the 100,000 bits and even the 250,000 bits per chip mark in the near future with yields and costs of equal or better than silicon semiconductor memories,

j On the other hand, the most optimistic available reports do not predict that magnetic

|| bubble memories can approach semiconductors in operating speed. Therefore, bubbles

i are thought to supplement semiconductor LSI chips in future electronic systems rather

jj than to displace them.

] The application of the bubble device was found to occur first as memory in space

and military digital data recorders. This memory application makes use of the highreliability (no moving mechanical parts), high data-storage-density, low-power-operation,

, and high-radiation-resistance characteristics of the garnet bubble devices. Future

li applications that are found in bubble device evaluation reports include desk calculators,

j hand-held calculators, computer peripherals (disk and drum memories), microminiature bubble

' displays, and electronic test and measurement devices. Little information was found on

: the application of magnetic bubble devices other than memory.

31
According to recent advertisements and publications, the introduction of magnetic

bubble memory devices promises a significant impact on electronics systems--especial ly

computers. According to the information contained in Table 4, it appears that

manufacturers in Japan, Great Britain, and France are realizing this potential and are gearing up for mass production of magnetic domain memories. Technology forecaster

reports, however, are contradictory over the time when bubble memories §re to catch on. The more optimistic forecasters claim that garnet bubble device acceptance should take

place within the next two to five years.

32
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33
5. GLOSSARY

Glossary of Terms Applicable to Magnetic Bubble Technology

Amorphous film - a film with a noncrystalline structure.

Angel fish - a bubble guide pattern consisting of a series of permalloy arrowheads by

which bubbles are propagated directly in response to the modulation of an external

magnetic field which is applied normal to the chip surface.

Bubble - an isolated cylindrical domain which exhibits various magnetic properties.

Bubble device - an independent unit (such as memory or a logic processor) wherein

the bubble is the active element.

Bubble host - a material such as a thin-film magnetic garnet epitaxial ly grown on a nonmagnetic garnet substrate. When exposed to the proper magnetic fields normal

to the film surface, the garnet film can sustain small stable areas of reverse magnetization, referred to as bubble domains.

Bubble memory - a storage device in which magnetic bubbles are the active elements.

Coercivity - the characteristic of magnetic material which opposes the demagnetizing

effect of an external magnetic field.

Conductor access - a method involving conductors in which currents in the conductors

generate the required fields for magnetic bubble propagation.

Direct-optical sensing - a method in which the detector reacts to changes in the

intensity of light caused by the passage of a bubble over a light source.

Domain wall - the boundary separating adjacent magnetic domains, which is the

transition zone through which the magnetization reverses direction.

Electromagnetic-induction detection - a detection method in which the bubble serves

as a tiny moving magnet dipole that induces a voltage in a pickup loop located in

the reading head.

Epitaxy - a controlled growth or deposition of a crystalline material having the same

crystal orientation as the substrate onto which the deposition is formed.

Evaporation - a process by which alloys are formed when beams of thermally agitated

atoms intermingle and condense on the underside of a substrate that is suspended

in their paths, each beam rising from a heated dish containing a liquid from one of the elements of which the alloy is composed.

Field-access - a method for propagating bubbles by the use of an external pulsating

or rotating magnetic field.

Gal vano-magnetism/Electromagnetism - magnetism developed by the flow of electrical

current

.

34
Garnet - any hard vitreous crystalline mineral from a group comprised of silicates of

calcium, magnesium, iron, or manganese with aluminum or iron. For magnetic bubbles,

any material h-nving a garnet-like crystal structure with a formula of (A) 3 Fes ^12^

where A is a material such as yttrium or one of the rare earths.

Hall effect detection - a phenomenon in which a voltage appears across a semiconductor

slab carrying a direct current when the magnetic field of the bubble acts

perpendicularly to the slab (at right angles to the current).

Hexagonal ferrite - any phase containing Fe and having a crystal structure related

to, but not necessarily the same as, magnetopl umbite.

In-plane rotation - a rotating magnetic field which is applied parallel to the surface

of a magnetic platelet containing bubbles.

Liquid phase epitaxy (LPE) - a process of developing magnetic materials, such as garnets, by dipping a non-magnetic crystal into a solution so that a magnetic

epitaxial film or solute crystal grows on the surface of the substrate.

Magnetic thin film - a layer of magnetic material on the order of one micron thick.

Magnetopl umbite - Pb Fei2 O19 any phase, containing Fe, having a similar crystal

structure.

Magnetoresistance - the effect in which a change in electrical resistance of a material occurs which results from the presence of a magnetic field.

Magnetorestrictivity - the effect or phenomenon in which a magnetic material develops

mechanical strains or stresses when magnetized.

Nonvol atil ity - a property of storage media indicating a capability of information

retention independent of sustained power application.

Nucleation - the formulation of a nucleus or the process of clustering.

Oersted - the oersted (CGS system) is the intensity of a magnetic field in which a unit magnet pole experiences a force of one dyne.

Orthoferrite - generally, a mineral consisting of imn and other materials with an orthorhombic distortion of the perovskite crystal structure, whose chemical formula

is A Fe O3 where A can be any rare earth material such as gadolinium.

Permalloy - a bubble guide material, usually consisting of nickel-iron alloy (Ni Fe),

which is deposited on a magnetic material.

Photolithography - a process of depositing images by usinq photographic techniques.

Sputtering - a process by which groups of atoms are chipped away by impact of material

from the surface of a target material having the same composition as that of the

desired alloy film, and fall onto a substrate, thus building up the layer of an alloy film.

35
T-bar - a bubble guide pattern which consists alternately of "T" or "I" shaped

patterns of permalloy which are deposited on a magnetic material.

Uniaxial structure - a crystalline configuration wherein the magnetic moment vectors

are all aligned in the same direction along an easy axis.

Wafer - a thin platelet of material such as a slice of silicon, germanium, or garnet.

Y-bar - a bubble guide pattern which consists of permalloy Y's and bars alternately

deposited on a magnetic material.

Glossary of Memory Terms

Access time - the time between input memory addressing and output information

availabil ity.

Angstrom - a unit of measurement of wavelength equal to 10"'* micrometer or 10"^

centimeter.

Associative memory - a memory which produces addresses of words based on the contents

of words, rather than the contents of words based on addresses of words; also

referred to as content-addressable, catalog, or search memory.

B-H curve - a plot of flux density (B) versus magnetizing force of a magnetic material

which shows the characteristic hysteresis loop.

Bipolar memory - a memory in which the storage element utilizes devices such as transistors whose conduction involves both minority and majority carriers.

Bit density - a measure of the number of bits stored per unit of length or area in

the storage medium.

Bit plane - a screen or 2-dimensional surface each layer of which contains one bit

associated with many words.

Block transfer - the transmission of a group of consecutive words considered as a unit

from one plane to another.

Cache - a high-speed memory whose contents are continually updated in blocks from a larger, slower memory to make the effective memory access time approach that of the

higher speed (cache) memory.

Charge-coupled device - a semiconductor device which propagates signals by the

movement of charge packets,

CMOS (Complementary-iletal -Oxide-Semiconductor) - circuitry and logic employing both

P-channel and N-channel MOS transistors with opposite, or complementary, switching

characteristics.

Coincident current selection - the addressing, or selection, of a magnetic memory

element for reading or writing by the simultaneous drive from two or more current

sources

.

Content addressable memory - (see associative memory).

36
Core - a magnetic toroid, usually a ferrite, capable of being magnetized and remaining

in one of two conditions of magnetization, thus capable of providing information

storage.

Destructive readout - a reading process that destroys the information that has been

read out.

Direct access - a method which access to the next piece of information is not dependent upon the last accessed source of information.

Dynamic cell - a storage cell where stored information is affected by time.

Easy axis of magnetization - a preferred direction of magnetization in a magnetic

material. '

ECL (Emitter-Coupled Logic) - a nonsaturated structure logic where the multiple gate

inputs are coupled together by their respective emitters.

Error rate - the total number of errors divided by the total number bits transmitted.

Flux density - the number of magnetic lines of force passing through a unit area.

Full-select current - the total current required in a selection winding or windings

through a magnetic core to saturate the core.

Half-select current - approximately one-half the total current required in a winding

or windings through a magnetic core to saturate the core.

Hard-axis of magnetization - a direction of magnetization perpendicular to the easy

axis of magnetization of a material.

Head gap - the spacing in the magnetic circuit of a record/reproduce head from which

the fringing fields emanate.

Hysteresis loop - a graph showing a plot of flux density in a magnetic material on the

ordinate and the magnetizing force which produces the flux on the abscissa.

Latency - a delay time in accessing information from a storage device.

Logic speed - the typical logic gate-to-gate propagation speed or clock rate.

LSI (Large-Scale-Integration) - a silicon (or other material) chip containing many

gates.

Mass memory - storage devices such as drums, disks, tapes, etc., which are capable of

storing large quantities of information.

Memory bus - one or more conductors used as a path over which information may be

transmitted from any of several memories to any of several computer system

destinations

.

Memory capacity - the number of bits, bytes, words, or other elementary quantity of

data that can be stored in a memory device.

37
Memory port - an interface allowing access to the contents of a memory.

MOS (Metal -Oxide-Semiconductor) - a field-effect transistor where the gate is

insulated from the channel between source and drain by a metal oxide.

MTBF - "Mean-Time-Between-Fail ures" (abbreviation).

MTTR - "Mean-Time-To-Repai r" (abbreviation).

Nondestructive readout - the sensing of information contained in a storage device

without significantly changing the physical representation of the stored information

Paging - the grouping of storage segments by page and transferring these pages back

and forth between main memory and the slower, larger backup memory.

Partial switching - the flux change in a core resulting from the application of

partial read or partial write pulses.

Plated wire memory - memories which are obtained by depositing a material such as permalloy in the form of thin-film on a wire.

PROM (Programmable-Read-Only-Memory) - a memory having factory or user programmed

contents which are only capable of being read.

RAM (Random-Access-Memory) - a memory capable of being addressed in any sequence for

either reading or writing.

Remanent magnetization - the state of magnetization of a material after the external

magnetic field has been removed.

ROM (Read-Only-Memory) - a memory having preprogrammed contents capable of being

sensed or read only.

Saturation - the magnetic state of a material beyond which an increase in the

magnetization is not possible.

Semiconductor memory - a memory whose basic storage elements are semiconductor

devices.

SOS (Sil icon-On-Saphire) - a metal -oxide-semiconductor circuit developed on an insulator (sapphire) base.

Thin-film memory - a memory that utilizes magnetic thin-films deposited on materials

such as glass.

Transfer rate - the rate at which elements of information are transmitted in sequence

from source to destination.

TTL (Transistor-Transistor Logic, or T^L logic) - a standard integrated logic

structure consisting of interconnected transistors.

Virtual storage - a combination of hardware and software which automatically allows

programmers to program the combination main memory and mass memory as if they were one large main memory.

Volatile storage - a memory device which loses data when power is removed.

38
6. REFERENCES

1. Gianola, U.F., D.H. Smith, A. A. Thiele, and L.G. Van Uitert, "Material Requirements

for Circular Magnetic Domain Devices," in IEEE Transactions on Magnetics , Mag 5:3

(September 1969), pp. 558-561, 21 refs.

2. Thiele, A. A., "Theory of the Static Stability of Cylindrical Domains in Uniaxial

Platelets," in Journal of Applied Physics , 41:3 (March 1, 1970), pp. 1139-1145,

18 refs.

3. Levine, D. , "Magnetic bubbles," in Electronics Australia , 34:10 (January 1973),

pp. 12-15, 1 ref.

4. Pierce, R.D., "CRYSTALLOGRAPHIC CONSIDERATIONS IN THE USE OF CUBIC MATERIALS WITH

INDUCED ANISOTROPIES IN BUBBLE DOMAIN DEVICES," AIP Conference Proceedings No. 5 , (1971 ), pp. 146-149, 8 refs.

5. Bobeck, A.H., "Properties and Device Applications of Magnetic Domains in Orthoferrites ," in The Bell System Technical Journal , Volume XLVI, No. 8 (October 1967) pp. 1901-1925, 8 refs.

6. "Memories - Bubbles are in the air," in Electronics , 48:13 (June 26, 1975), p. 68.

7. Little, A.D., Inc., "Technology and Cost Forecasts for Electronic Data Processing

Hardware, Software and Data Communication Networks," Cambridge, Massachusetts,

(Prepared for U.S. Air Force, Air Force Systems Command, Electronic Systems

Division), (Contract No. F19628-74-C-0093, SADPR-85, 15 February 1974),

pp. 2-1 to 2-24.

8. Gayner, A.H., "BUBBLE MEMORIES - WHAT IS THE SIGNIFICANCE?," in A Note Service

Report for L. F. Rothschild and Company, (June 6, 18, and 19, 1975).

9. Wolfe, R. , and J.C. North, "Supression of Hard Bubbles in Magnetic Garnet Films by

Ion Implantation." in The Bell System Technical Journal . (July-August 1972),

pp. 1436-1440, 8 refs.

10. Chang, H,, "Capabilities of the bubble technology." in AFIPS Conference Proceedings - 1974, Vol. 43 (1974), pp. 847-855, 34 refs.

11. Marvel, O.E., "MEMORY TECHNOLOGIES AND SYSTEMS FOR THE MID-70' s." in Computing in the

Mid-70' s: An Assessment ," Fourteenth Annual Technical Svmoosium sponsored by ACM,

(June 19, 1975), pp. 49-53.

12. "Hitachi Readies Bubble Memory Line," in Electronic News , 20:1050 (October 20, 1975),

p. 61.

13. "Plessey plans line of magnetic bubble memories," in Electronics , 48:15,

(July 24, 1975), p. 55.

14. "Memory: French introducing domain memory," in Electronics , 48:6, (March 20, 1975),

pp. 32-34.

15. "Magnetic Bubbles Moving at 500 m/s Can Increase Recording Frequency," in Computer

Design , 14:2 (February 1975), p. 50.

39
16. Parzefall , F. , "Magnetic Bubbles, a Memory Principle Promising for the Future," in

Electronik , 23:2 (1974, written in German), pp. 39-42, 8 refs.

17. "460 KBIT BUBBLE MEMORY ACCESSES IN 2.7 Ms.," in Digital Design , 4:9 (September 1974),

p. 12.

18. Bobeck, A.H., P.I. Bonyhard, and J.E. Geusic, "Magnetic Bubbles - An Emerging New

Memory Technology," in Proceedings of the IEEE , 63:8 (August 1975), pp. 1176-1195,

57 refs.

19. "Density pushed by bubble lattice," in Electronics , 47:26 (December 26, 1974), p. 25.

20. "Domain memory tops 2 megabits," in El ectronics , 47:25 (December 11, 1975), p. 36.

21. Bobeck, A.H., R.F. Fischer, A.J. Perneski , J. P. Remeika, and L.G. Van Uitert

"Applications of Orthoferrites to Domain-Wall Devices," in IEEE Transactions on Magnetics , Mag 5:3 (September 1969), pp. 544-553, 18 refs.

22. Adam. J.D.. J.M. Owens, and J.H. Collins, "FERROMAGNETIC-RESONANCE LINEWIDTH OF THICK

YTTRIUM- IRON-GARNET FILMS GROWN BY LIQUID-PHASE EPITAXY," in Electronics Letters , 9:15 (July 26, 1973), p. 325, 4 refs. ~

23. Geiss, E.A., B.E. Argyle, D.C. Cronemeyer, E. Klokholm, T.R. McGuire, D.F. O'Kane,

T.S. Plaskett, and V. Sadagopan, "EUROPIUM- YTTRIUM IRON-GALLIUM GARNET FILMS GROWN BY LIQUID PHASE EPITAXY ON GADOLINIUM GALLIUM GARNET," in AIP Conference Proceedings : i' Magnetism and Magnetic Material s-1 971 , 5:1, (American Institute of Physics, ~~

New York) pp. 110-114, 16 refs.

24. Hidaka, Okada, Suzuki, Matsumi , and Hibiya, "Yttrium-Europium Iron-Gallium Garnet

Single Crystals for Bubble Domain Devices," in Japan Journal of Applied Physics ,

1 3:5 (1974), pp. 903-904, 3 refs. I'

25. Plaskett, T.S., E. Klokholm, H.L. Hu, and D.F. O'Kane, "MAGNETIC BUBBLE DOMAINS IN (EuY)3 Fe5Qi2 FILMS ON Sm^ Ga^ Oj, SUBSTRATES," in AIP Conference Proceedings:

Magnetism and Magnetic Material s-1 972 , 10:1, (American Institute of Physics,

New York, 1973), pp. 319-323, 5 refs.

26. Takeuchi , Hiroshi, Kohsei Shinagawa, and Satoshi Taniguchi, "Faraday Effect of

Bi-Substituted Rare-Earth Iron Garnet," in Japan Journal of Applied Physics , 12:3

(1973), p. 465, 1 ref. '

27. Tolksdorf, W. , "Magnetic garnet single crystal growth from fluxed melts," in

Acta Electronica , 17:1 (January 1974), pp. 57-67, 59 refs.

28. Chaudhari , P., J.J, Cuomo, and R.J. Gambino, "Amorphous Metallic Films for Bubble ' Domain Applications," in IBM Journal of Research and Development . 17:1

(January 1973), p. 66-68, 8 refs.

29. "Amorohous films and magnetic bubbles," in IBM Computing Report, 9:2 (Summer 1973). ! p, 12. =

[

30. "Magnetic bubbles observed in evaporated amorphous films," in EDN . 19:24

(December 20, 1974), pp. 12-13.

40
31. Kryder, M.H., K.Y. Ahn, G.S. Almasi, G.E. Keefe, and J.V. Powers, "BUBBLE TO T-I BAR COUPLING IN AMORPHOUS FILM SMALL BUBBLE DEVICES," in an IBM Research Paper (RC4847) , #21373 (April 15, 1974), 4 p., 5 refs.

32. Bobeck, A.H., R.F. Fischer, and A.J. Perneski, "A new approach to memory and

logic-cylindrical domain devices," in AFIPS Conference Proceedings 1969 , (Bell

Telephone Laboratories, Murray Hill, New Jersey) Vol. 35 (Fall 1969), pp. 489-198,

10 refs,

33. Tsurushima, Toshio, Yoshinobu Sugiyama, Hisao Tanoue, Hideo Yamada, and Shoei Kataoka,

"APPLICATION OF SELECTIVE ION IMPLANTATION TO MAGNETIC BUBBLE DEVICES," in

Supplement to the Journal of the Japan Society of Applied Physics , Vol. 43 (1974),

(Proceedings of the 5th Conference - 1973 International - on Solid State Devices,

Tokyo, 1973), pp. 464-470, 6 refs.

34. Rooymans, CJ.M., "Growth and application of single crystals on magnetic oxides,"

in Acta Electronica , 17:1 (January 1974), pp. 33-44, 43 refs.

35. Bonyhard, P.I., J.E. Geusic, A.H. Bobeck, Yu-Ssu Chen, P.O. Michaelis, and J.L. Smith,

"Magnetic Bubble Memory Chip Design," in IEEE Transactions on Magnetics , Mag 9:3

(September 1973), pp. 433-436, 15 refs.

36. Bosch, L.J., R.A. Downing, G.E. Keefe, L.L. Rosier, and K.D. Terlep, "1024 Bit Bubble

Memory Chip," in IEEE Transactions on Magnetics , Mag 9:3 (September 1973),

pp. 481-484, 9 refs.

37. Hewitt, B.S.. R.D. Pierce, S.L. Blank, and S. Knight, "Technique for Controlling the

Properties of Magnetic Garnet Films," in IEEE Transactions on Magnetics , Mag 9:3

(September 1973), pp. 366-372, 25 refs.

38. Varnerin, L.J., "Approaches for Making Bubble-Domain Materials," in IEEE Transactions

on Magnetics , (September 1971). pp. 404-409, 22 refs.

39. Bonyhard, P. I., I. Danylchuk, D.E. Kish, and J.L. Smith, "Applications of Bubble

Devices," in IEEE Transactions on Magnetics , Mag 6:3 (September 1970), pp. 447-451,

5 refs.

40. Beausoleil , W.F., D.T. Brown, and B.E. Phelps, "Magnetic Bubble Memory Organization,"

in IBM Journal of Research and Development , 16:6 (November 1972), pp. 587-591,

6 refs.

41. Karp, H.R., "Magnetic bubbles - a technology in the making," in Electronics , 24:18,

(September 1, 1969), pp. 83-87.

42. "Japan Subsidizes Bubble Memories," in Electronic News , 19:986 (July 29, 1974) p. 53.

43. Shinagawa, Kohsei, Hiroshi Takeuchi , and Satoshi Taniguchi, "Lead-Substituted Yttrium

Iron Garnets and Their Anomalous Faraday Rotation," in Japan Journal of Applied

Physics , 12:3 (1973), o. 466, 4 refs.

44. "Large Magnetic Bubble Material Uniform in Magnetic Characteristics - KDD Research

Lab," in Journal of Electronic Engineering , (Japan, February 1975), pp. 58-59.

41
45. "HITACHI PERFECTS SUPERIOR MAGNETIC BUBBLE MEMORY DEVICE," in Tokyo NIHON KEIZAI SHINBUN , (August 11, 1975), p. 10.

46. Nakanishi, H., and C. Uemura, "A New Type of Bubble Motion in Magnetic Garnet Films,"

in Japan Journal of Applied Physics , 13:1 (1974), pp. 191-192, 2 refs.

47. Yoshizawa, Shigeru, Naoki Yamamoto, Hirofumi Ota, Tetsu Oi , Junji Shigeta, and

Gen-Ichi Kamoshita, "Small Bubble Domain Detection by Hall Effect of InSb Films,"

in IEEE Transactions on Magnetics , (September 1972), pp. 554-557, 8 refs.

48. Darby, M.I., "CONCERNING THE THEORY OF BUBBLE DOMAINS WITH NEEL WALLS," in International Journal of Magnetism , 4:3 (1973), pp. 199-204, 6 refs.

49. Allan, R.S., "Coming in computer memories: semis plus magnetic domains," in Electronic

Design , Vol. 25 (December 9, 1971), pp. 22 and 24.

50. De Jonge, F.A., W.F. Druyvesteyn, A.G.H. Verhulst. "MULTIPLE HYSTERESIS OF A HOLLOW

CYLINDRICAL DOMAIN," in International Journal of Magnetism , Vol, 2 (1972),

pp. 7-13, 4 refs,

51. Bobeck, A.H., I. Danylchuk, F.C. Rossol , and W. Strauss, "Evolution of Bubble Circuits

Processed by a Single Mask Level," in IEEE Transactions on Magnetics , Mag 9:3

(September 1973), pp. 474-480, 13 refs.

42
NBS-n4A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUULK ATION OR REPORT NO. NBS SP 500-1

2. Gov't Accession

No.

3. Recipient's Acccs.sion No.

4. TITLE AND SUBTITLE

COMPUTER SCIENCE & TECHNOLOGY:

Foreign and Domestic Accomplishments in Magnetic

Bubble Device Technology

5. Publication Date January 19??

6. Performing Organization (.ode

7. AUTHOR(S)

Robert B. J. Warnar and Peter J. Calomeris

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proiect/Task/Work Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as Item 9

13. Type of Report & Period Covered Final 1967-1975

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

Japanese, Western European, and U. S. capabilities in Magnetic Bubble Device

Technologies are described. Library of Congress Catalog Card Number: 76-6O8386

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This document assesses the status of magnetic bubble technology as displayed

by non-U. S. research and manufacturing facilities. Non-U. S. research and U.S.

accomplishments are described while both technical and economic factors are addressed. Magnetic bubble devices are discussed whenever their application

could impact future computer system design. Generally the magnetic bubble

device can be applied to a computer system as a peripheral mass memory.

Magnetic bubble devices are produced from either synthetic garnet or amorphous

materials rather than from familiar silicon material. The document contains

a significant bibliography to support certain main points which are supplemented by information supplied by the library of the Information

Technology Division (ICST-NBS) and from private interviews with various U. S. technical experts.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Amorphous materials; bubble; field-access; garnet; guide-pattern; magnetore si stance

nonvolatility; orthoferrite; photolithograpty; uniaxial structures

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