Magnetic Bubble Technology

327 Pages·1980·5.685 MB·English

by  Andrew H. Eschenfelder PhD (auth.)

Conversion of Gaussian to Sf Units
Fundamental Gaussian SI Ratio·
quantity
SI
Symbol Units Symbol Units
Gaussian
Magnetization 41tM G M A/m 103/4n
Permeability of - - ,uo =4n x 10-7 Wb/Am 41l x 10-7
free space
Anisotropy K erg/em 3 K J/m3 10-1
Exchange A erg/em A J/m 10-5
Gyromagnetic ratio y (s·Oe)-1 y (s.A/m)-l 41l/103
Gilbert parameter rx - rx - 1
Parameter Defining Units Defining Units Ratio·
formula formula
Magnetic field H SH.dl=41lNI/10 Oe SH·dl=NI A/m 103/41l
strength
Magnetic induction B B=H+41tM G B=,uo(H +M) Wb/m2 10-4
Flux 4> 4>= SB.dA Mx 4>= SB.dA Wb 10-8
Energy product BH/81l=>MH/2 erg/em 3 BH/ 2 => ,uoM H /l J/m3 10-1
Demagnetization N Hd= -NM - Hd=-NM - 1/41l
factor
Volume X,K X=dM/dH - K=dM/dH - 41l
susceptibility
Permeability ,u ,u=dB/dH - ,u=dB/dH - 41lX 10-7
= 1 +41lX =,uo(1 + K) =,uo
Anisotropy field HK HK=2K/M Oe HK=2K/,uoM A/m 103/41l
Stability factor Q Q=HK/41lM - Q=HK/M - 1
Wall energy (J (J=4t!AK erg/cm2 (J=4t!AK 1/m2 10-3
density
Characteristic I 1= (J/41lM2 em 1=(J/,uoM2 m 10-2
length
W 1'W
Wall mobility ,uR, ,uR,= l' cm/s·Oe ,uR,= m2/s·A 41lxl0-5
rx K rx K
m meter s second A Ampere Oe Oersted G Gauss
em centimeter N number of turns J Joule Wb Weber Mx Maxwell
* To obtain values in SI units multiply value in Gaussian units by the respective ratio
14 Springer Series in Solid-State Sciences
Edited by Hans-Joachim Queisser
Springer Series in Solid-State Sciences
Editors: M. Cardona P. Fulde H.-J. Queisser
Volume 1 Principles of Magnetic Resonance 2nd Edition 2nd Printing
By C. P. Slichter
Volume 2 Introduction to Solid-State Theory
By O. Madelung
Volume 3 Dynamical Scattering of X-Rays in Crystals
By Z. G. Pinsker
Volume 4 Inelastic Electron Tunneling Spectroscopy
Editor: T. Wolfram
Volume 5 Fundamentals of Crystal Growth I. Macroscopic Equilibrium
and Transport Concepts
By F. Rosenberger
Volume 6 Magnetic Flux Structures in Superconductors
By R. P. Huebener
Volume 7 Green's Functions in Quantum Physics
By E. N. Economou
Volume 8 Solitons and Condensed Matter Physics
Editors: A. R. Bishop and T. Schneider
Volume 9 Photoferroelectrics
By V. M. Fridkin
Volume 10 Phonon Dispersion Relations in Insulators
By H. Bilz and W. Kress
Volume 11 Electron Transport in Compound Semiconductors
By B. R. Nag
Volume 12 The Physics of Elementary Excitations
By S. Nakajima
Volume 13 The Physics of Selenium and Tellurium
Editors: E. Gerlach and P. Grosse
Volume 14 Magnetic BubbleTechnology
By A. H. Eschenfelder
Volume 15 Modem Crystallography I. Crystal Symmetry, Methods
of Structural Crystallography
By B. K Vainshtein
Volume 16 Electronic States in Organic Molecular Crystals
By E. A. Silinsh
A. H. Eschenfelder
Magnetic Bubble
Technology
With 271 Figures
Springer-Verlag Berlin Heidelberg New York 1980
Andrew H. Eschenfelder, PhD
IBM Research Laboratory, 5600 Cottle Road
San Jose, CA 95193, USA
Series Editors:
Professor Dr. Manuel Cardona
Professor Dr. Peter Fulde
Professor Dr. Hans-Joachim Queisser
Max-Planck-Institut fUr Festkorperforschung
Heisenbergstrasse 1, D-7000 Stuttgart 80, Fed. Rep. of Germany
ISBN-I3: 978-3-642-96551-7 e-ISBN-13: 978-3-642-96549-4
001: 10.1007/978-3-642-96549-4
Library of Congress Cataloging in Publication Data. Eschenfelder, Andrew H., 1925-. Magnetic bubble
technology. (Springer series in solid-state sciences; v. 14). Bibliography: p. Includes index.!. Magnetic bubbles. 1.
Title. II. Series. QC754.2.M34E8 538'.3 79-24651
This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned,
specifically those of translation, reprinting, reuse of illustrations, broadcasting, reproduction by photocopying
machine or similar means, and storage in data banks. Under § 54 ofthe German Copyright Law, where copies are
made for other than private use, a fee is payable to the publisher, the amount of the fee to be determined by
agreement with the publisher.
© by Springer-Verlag Berlin Heidelberg 1980
Softcover reprint of hardcover I st edition 1980
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific
statement, that such names are exempt from the relevant protective laws and regulations and therefore free for
general use.
2153/3130-543210
This book is dedicated to
all of the men and women who have worked
so diligently and competently to make the
magnetic bubble technology a practical reality
and to produce the knowledge that is
presented herein
Preface
Magnetic bubbles are of interest to engineers because their properties can be
used for important practical electronic devices and they are of interest to
physicists because their properties are manifestations of intriguing physical
principles. At the same time, the fabrication of useful configurations challenges
the materials scientists and engineers. A technology of magnetic bubbles has
developed to the point where commercial products are being marketed. In
addition, new discovery and development are driving this technology toward
substantially lower costs and presumably broader application. For all of these
reasons there is a need to educate newcomers to this field in universities and in
industry.
The purpose of this book is to provide a text for a one-semester course that
can be taught under headings of Solid State Physics, Materials Science,
Computer Technology or Integrated Electronics. It is expected that the student
of anyone of these disciplines will be interested in each of the chapters of this
book to some degree, but may concentrate on some more than others,
depending on the discipline. At the end of each chapter there is a brief summary
which will serve as a reminder of the contents of the chapter but can also be
read ahead of time to determine the depth of your interest in the chapter.
The level of technical detail in each chapter has been intentionally restricted
to satisfy the purpose of the book as a one-semester course. The references given
for each chapter provide additional reading for those interested in greater depth
in the subjects covered.
The first chapter serves as an introduction to the field of magnetic bubbles
technology and can be read in order to gain an overall perspective of the field
and an understanding ofthe scope and organization ofthe rest of the book. The
subsequent chapters describe the properties of magnetic bubbles and their
physical origin; the materials that are suitable for bubbles and the way that
these materials are prepared; the different forms of devices that have been made
using bubbles and the way that these devices operate; the relationship of the
practical device parameters to the fundamental magnetic characteristics of
bubble materials; applications for bubble devices and examples of product
configurations for those applications and a discussion of the future prospects
for magnetic bubble science and technology.
The preparation of this book has been facilitated by a substantial grant of
time and assistance by the IBM Corporation for which the author is extremely
grateful.
San Jose, California, November 1979 A. H. Eschenfelder
Contents
1. Introduction to Magnetic Bubbles
1.1 What Are Magnetic Bubbles? 1
1.2 Available Bubble Materials . 3
1.3 How Can Bubbles be Manipulated? 5
1.4 Why Are Bubbles of Practical Interest? 8
1.5 A Typical Storage Device . . . . . . 11
1.6 Why Are Bubbles of Scientific Interest? 15
1.7 Scope and Organization of the Book 16
1.8 History . 17
1.9 Summary. . . . . . . . . . . 18
2. Static Properties of Magnetic Bubbles 19
2.1 Fundamental Characteristics of the Bubble Film 19
2.1.1 Magnetic Interactions . . . . . . . . 19
a) Exchange Energy Density, Ex . . . 20
b) Demagnetization Energy Density, ED 21
c) Anisotropy Energy Density, EK 22
d) Magnetic Field Energy Density. . . 22
e) Magnetoelastic Energy Density, Es . 23
2.1.2 Structural Characteristics of the Bubble Film 24
2.1.3 Anisotropy Energy Density . . . . . . . 24
a) Growth Anisotropy Density, E~ . . . . 24
Ei
b) Crystalline Anisotropy Energy Density, 25
2.1.4 Summary ofImportant Film Parameters 27
2.2 Bubble Domain Configurations . . . . 27
2.2.1 Equilibrium Configuration
ofa Small Segment of Domain Wall 28
2.2.2 Equilibrium Configuration of an Isolated Bubble 30
2.2.3 Influence of Permalloy Overlayers . . . . . . 44
2.2.4 Equilibrium Configuration of a Bubble Lattice 46
2.2.5 Bubble States 48
2.2.6 Hard Bubbles 50
2.3 Summary. . . . . 54
3. Dynamic Properties of Magnetic Bubbles 57
3.1 Motion of a Wall 57
3.1.1 Description of Planar Wall Segments 57
X Contents
3.1.2 Motion of an Uncoupled Magnetic Moment . . .. 60
3.1.3 Equation of Motion for a Planar Domain Wall Segment 62
3.1.4 Motion of an Infinite Planar Wall Without Bloch Lines 63
3.1.5 Motion of a Planar Wall Without Bloch Lines in a Film
of Thickness, h . . . . . . . . . . . . . . 65
3.1.6 Motion of a Bloch Line in a Moving Bloch Wall 67
3.1.7 Summary of the Motion of Planar Walls 69
3.2 Motion of a Bubble . . . . . . . 70
3.2.1 Bubble Mobility . . . . . . . . . . 70
3.2.2 Gyrotropic Bubble Deflection . . . . 71
3.2.3 Response of Bloch Lines to Bubble Motion 73
3.2.4 The Influence of the Film Surface 74
3.2.5 Bloch Line Phenomena . . . . . . . 76
3.2.6 Influence of a Surface Cap . . . . . . 80
3.2.7 Influence of Orthorhombic Anisotropy 83
3.3 Summary . . . . . . . . . . . . . . . . 84
4. Basic Permalloy-Bar Bubble Devices 87
4.1 Propagation ........ 87
4.1.1 TI Bar Propagation Model 88
4.1.2 TI Bar Propagation Margins 95
4.1.3 C Bar Propagation Margins 100
4.1.4 Failure Mechanisms in C Bar Propagation 105
4.2 Other Functional Elements 106
4.2.1 Generators. 106
4.2.2 Switches. . . . . 108
4.2.3 Sensors . . . . . 112
4.3 Total Chip Performance 116
4.4 Device Scaling 118
4.5 Summary. . . . . . 119
5. Other Bubble Device Forms 121
5.1 Two-Level Permalloy Bar 121
5.2 Charged-Wall Bubble Devices 122
5.2.1 CD Propagation . . . 123
5.2.2 Propagation on Ion-Implanted CD Patterns 126
5.2.3 The Influence of Anisotropy in the Implanted Layer 129
5.2.4 The Influence of Pattern Geometry 136
5.2.5 Other CD Device Functions . . . . . . . 137
5.3 Bubble Lattice Devices . . . . . . . . . . . . 138
5.3.1 Review of Salient Features of Lattice Bubbles 139
5.3.2 Lattice Propagation . . 141
5.3.3 Other Lattice Functions . . . . . . . . . 148
Contents XI
5.4 Current Sheet Devices . . 151
5.4.1 Dual Conductor (DC) 153
5.4.2 Cross-Hatch (XH) 156
5.5 Summary. . . . . . . . 158
6. Bubble Materials 163
6.1 The General Approach to Tailoring the Properties
of Bubble Materials . . . . . . . . . . 165
6.2 Garnets . . . . . . . . . . . . . . . 171
6.2.1 Crystal Structure and Lattice Spacing 171
6.2.2 Magnetization . . . . . 173
6.2.3 Magnetic Anisotropy 180
6.2.4 Garnet Dodecahedral Sites 187
6.2.5 Dynamic Properties 195
6.2.6 Range of Garnet Properties 203
6.3 Hexaferrites. . . . . . . 205
6.3.1 Crystal Structure . . 205
6.3.2 Magnetic Properties 209
6.4 Amorphous Materials 210
6.4.1 Similarities and Differences 211
6.4.2 Static Properties . . . 213
6.4.3 Dynamic Properties . 219
6.4.4 Summary . 220
6.5 Orthoferrites . 221
6.6 Summary. . . . 221
7. Device Chip Fabrication . 225
7.1 Crystal Growth . . . 225
7.1.1 Choice of Substrates . 225
7.1.2 Czochralski Growth of Garnet Crystals 225
7.1.3 Critical Factors and Typical Values 226
7.2 Substrate Preparation 227
7.3 Film Growth . . . . . . . . 228
7.3.1 Film Growth Options . . 228
7.3.2 Dipping LPE Techniques 229
7.3.3 Crucial Factors and Potential Problems 230
7.3.4 Phenomena That Must be Understood and Controlled 231
7.3.5 Process Control . . . . 237
7.4 Fabrication of Device Structure 240
7.4.1 Typical Planar Process 243
7.4.2 Variations on the Process . 245
a) Process Variations in a Planar Structure 245
b) Hard Bubble Suppression . . . . . . . 245