Magnetic Bubble Technology

1. Introduction to Magnetic Bubbles.- 1.1 What Are Magnetic Bubbles?.- 1.2 Available Bubble Materials.- 1.3 How Can Bubbles be Manipulated?.- 1.4 Why Are Bubbles of Practical Interest?.- 1.5 A Typical Storage Device.- 1.6 Why Are Bubbles of Scientific Interest?.- 1.7 Scope and Organization of the Book.- 1.8 History.- 1.9 Summary.- 2. Static Properties of Magnetic Bubbles.- 2.1 Fundamental Characteristics of the Bubble Film.- 2.1.1 Magnetic Interactions.- a) Exchange Energy Density, Ex.- b) Demagnetization Energy Density, ED.- c) Anisotropy Energy Density, EK.- d) Magnetic Field Energy Density, EH.- e) Magnetoelastic Energy Density, ES.- 2.1.2 Structural Characteristics of the Bubble Film.- 2.1.3 Anisotropy Energy Density.- a) Growth Anisotropy Density, EKG.- b) Crystalline Anisotropy Energy Density, EKC.- 2.1.4 Summary of Important Film Parameters.- 2.2 Bubble Domain Configurations.- 2.2.1 Equilibrium Configuration of a Small Segment of Domain Wall.- 2.2.2 Equilibrium Configuration of an Isolated Bubble.- 2.2.3 Influence of Permalloy Overlayers.- 2.2.4 Equilibrium Configuration of a Bubble Lattice.- 2.2.5 Bubble States.- 2.2.6 Hard Bubbles.- 2.3 Summary.- 3. Dynamic Properties of Magnetic Bubbles.- 3.1 Motion of a Wall.- 3.1.1 Description of Planar Wall Segments.- 3.1.2 Motion of an Uncoupled Magnetic Moment.- 3.1.3 Equation of Motion for a Planar Domain Wall Segment.- 3.1.4 Motion of an Infinite Planar Wall Without Bloch Lines.- 3.1.5 Motion of a Planar Wall Without Bloch Lines in a Film of Thickness, h.- 3.1.6 Motion of a Bloch Line in a Moving Bloch Wall.- 3.1.7 Summary of the Motion of Planar Walls.- 3.2 Motion of a Bubble.- 3.2.1 Bubble Mobility.- 3.2.2 Gyrotropic Bubble Deflection.- 3.2.3 Response of Bloch Lines to Bubble Motion.- 3.2.4 The Influence of the Film Surface.- 3.2.5 Bloch Line Phenomena.- 3.2.6 Influence of a Surface Cap.- 3.2.7 Influence of Orthorhombic Anisotropy.- 3.3 Summary.- 4. Basic Permalloy-Bar Bubble Devices.- 4.1 Propagation.- 4.1.1 TI Bar Propagation Model.- 4.1.2 TI Bar Propagation Margins.- 4.1.3 C Bar Propagation Margins.- 4.1.4 Failure Mechanisms in C Bar Propagation.- 4.2 Other Functional Elements.- 4.2.1 Generators.- 4.2.2 Switches.- 4.2.3 Sensors.- 4.3 Total Chip Performance.- 4.4 Device Scaling.- 4.5 Summary.- 5. Other Bubble Device Forms.- 5.1 Two-Level Permalloy Bar.- 5.2 Charged-Wall Bubble Devices.- 5.2.1 CD Propagation.- 5.2.2 Propagation on Ion-Implanted CD Patterns.- 5.2.3 The Influence of Anisotropy in the Implanted Layer.- 5.2.4 The Influence of Pattern Geometry.- 5.2.5 Other CD Device Functions.- 5.3 Bubble Lattice Devices.- 5.3.1 Review of Salient Features of Lattice Bubbles.- 5.3.2 Lattice Propagation.- 5.3.3 Other Lattice Functions.- 5.4 Current Sheet Devices.- 5.4.1 Dual Conductor (DC).- 5.4.2 Cross-Hatch (XH).- 5.5 Summary.- 6. Bubble Materials.- 6.1 The General Approach to Tailoring the Properties of Bubble Materials.- 6.2 Garnets.- 6.2.1 Crystal Structure and Lattice Spacing.- 6.2.2 Magnetization.- 6.2.3 Magnetic Anisotropy.- 6.2.4 Garnet Dodecahedral Sites.- 6.2.5 Dynamic Properties.- 6.2.6 Range of Garnet Properties.- 6.3 Hexaferrites.- 6.3.1 Crystal Structure.- 6.3.2 Magnetic Properties.- 6.4 Amorphous Materials.- 6.4.1 Similarities and Differences.- 6.4.2 Static Properties.- 6.4.3 Dynamic Properties.- 6.4.4 Summary.- 6.5 Orthoferrites.- 6.6 Summary.- 7. Device Chip Fabrication.- 7.1 Crystal Growth.- 7.1.1 Choice of Substrates.- 7.1.2 Czochralski Growth of Garnet Crystals.- 7.1.3 Critical Factors and Typical Values.- 7.2 Substrate Preparation.- 7.3 Film Growth.- 7.3.1 Film Growth Options.- 7.3.2 Dipping LPE Techniques.- 7.3.3 Crucial Factors and Potential Problems.- 7.3.4 Phenomena That Must be Understood and Controlled.- 7.3.5 Process Control.- 7.4 Fabrication of Device Structure.- 7.4.1 Typical Planar Process.- 7.4.2 Variations on the Process.- a) Process Variations in a Planar Structure.- b) Hard Bubble Suppression.- c) Nonplanar Structure.- d) Additive Electroplating.- e) SLM.- f) CD.- 7.4.3 Lithography.- 7.4.4 Potential Problems.- a) Stress.- b) Permalloy Domain Effects.- c) Electromigration.- d) Chemical Interaction.- 7.5 Summary.- 8. Chip Packaging.- 8.1 The Storage Unit.- 8.2 The Storage Module.- 8.3 Limitations on Module Size.- 8.4 Data Integrity.- 8.5 Module Testing.- 8.6 Summary.- 9. Applications.- 9.1 Useful Features of Bubble Devices.- 9.1.1 Intermediate Cost/Speed.- 9.1.2 Major/Minor Loop Organization.- 9.1.3 Lack of Momentum.- 9.1.4 Ladder Organization.- 9.2 General Purpose Storage Units.- 9.3 Storage Hierarchies.- 9.4 Special Purpose Applications.- 9.4.1 Repertory Dialer.- 9.4.2 Speech Announcement.- 9.4.3 Text Editing.- 9.4.4 Flight Recorder.- 9.5 Summary.- 10. Future Prospects.- 10.1 Dependencies of the Module Attributes.- 10.2 Constraints on Active Chip Area.- 10.3 Constraints on Device Cell Density.- a) Resolution of the Device Pattern Exposure System.- b) Resolution of the Device Structure Fabrication Method.- c) Electromigration.- d) Bubble Material Properties.- 10.4 Constraints on Operating Frequency.- 10.5 Loop Length.- 10.6 Areas for Future Research.- 10.7 Summary.- 11. Recent Developments.- 11.1 Contiguous Disk Bubble Devices.- 11.1.1 Charged Wall Bubble Propagation.- 11.1.2 Other Device Elements.- 11.1.3 Complementary Permalloy Devices.- 11.2 Permalloy Bar Storage Chips.- 11.3 Garnet Uniaxial Anisotropy, Ku.- 11.3.1 Ku by Preferential Distribution on Iron Sites.- 11.3.2 High Ku Using Bi Ions.- 11.3.3 Ion-Implantation Modification of Ku.- 11.4 Summary.- References.