Magneto-Resistive and Spin Valve Heads (eBook)

Cover 1
Contents 8
Preface to First Edition 14
Preface to Second Edition 18
Chapter 1. B, H, and M Fields 24
Magnetic Field H and Magnetic Moment Fundamentals and Applications Fundamentals and Applications µ 24
Electron Spin 26
Exchange Coupling 28
Magneto-Crystalline Anisotropy K 29
Magnetization M 30
Magnetic Poles and Demagnetizing Fields 31
Flux Density B and Flux . 34
Chapter 2. The Writing Process 37
Write-Head Field 37
Written Magnetization Transition M(x) 40
Chapter 3. The Reading Process 44
Recording Medium Fringing Fields 44
Read-Head Flux 45
Output Voltage 46
Output Spectrum 47
Digital Output Pulse 47
Chapter 4. The Anisotropic Magneto-Resistive Effect 50
The Basic Effect 50
Magneto-Resistive Sensors or Elements 51
Magneto-Resistive Coefficient .p/p0 57
The Unique Properties of Permalloy 58
Chapter 5. The Giant Magneto-Resistive Effect 62
Superlattices 62
The Physics of the GMR Effect 66
Granular GMR Materials 70
Chapter 6. Vertical Biasing Techniques 73
Permanent Magnet Bias 73
Current Bias 74
Soft Adjacent Layer Bias 76
Double Magneto-Resistive Element 77
Self-Bias 78
Exchange Bias 79
The Barber-Pole Scheme 81
The Split-Element Scheme 82
The Servo-Bias Scheme 83
Chapter 7. Horizontal Biasing Techniques 87
Conductor Overcoat 88
Exchange Tabs 89
Hard Films 90
Closed Flux 91
MRH Initialization Procedures 91
Chapter 8. Hunt's Unshielded Horizontal and Vertical Anisotropic Magneto-Resistive Heads 95
The Unshielded Horizontal Head 97
The Unshielded Vertical Head 99
Single Magnetization Transition Pulse Shapes 101
Side-Reading Asymmetry 102
Chapter 9. Single-Element Shielded Vertical Magneto-Resistive Heads 104
The Function of the Shields 104
The MRE Shield Magnetic Transmission Line 107
Shielded MRH Output Voltage Spectra 110
Shielded MRH Designs 114
Chapter 10. Simple Spin Valve Giant Magneto-Resistive Heads 117
Chapter 11. Enhanced Spin Valves 123
Top and Bottom Spin Valves 123
Exchange Coupling Phenomena 124
Cobalt "Dusting" and CoFe Alloys 128
Spin Valve Biasing Effects 129
Unpinning Phenomena 132
Chapter 12. Synthetic Antiferro- and Ferrimagnets 134
In the Pinned Layer 134
In the Free Layer 138
Chapter 13. Antiferromagnet Upsets 141
Chapter 14. Flux-Guide and Yoke-Type Magneto-Resistive Heads 144
Flux-Guide MRHs 145
Yoke-Type MRHs 146
Chapter 15. Double-Element Magneto-Resistive Heads 148
Classification of Double-Element MRHs 149
Advantages of Double-Element MRHs 152
General Comments 153
Chapter 16. Comparison of Shielded Magneto-Resistive Head and Inductive Head Outputs 155
Small-Signal Voltage Spectral Ratio 155
Large-Signal Voltage Comparison 157
Chapter 17. Simplified Design of a Shielded Anisotropic Magneto-Resistive Head 161
The Written Magnetization Transition 161
Inductive and Shielded MRH Output Pulses 163
The MRE Thickness T 164
The MRE Depth D 165
The Measuring Current I 166
The Isolated Transition Peak Output Voltage d V 167
Optmized MRH versus Inductive Head Voltages 168
Chapter 18. Simplified Design of a Shielded Giant Magneto-Resistive Head 170
The Written Magnetization Transition 170
Inductive and Shielded GMRH Output Pulses 172
The MRE Thickness T 173
The MRE Depth D 174
The Measuring Current I 175
The Isolated Transition Peak Output Voltage d V 175
Future Projections 176
Chapter 19. Read Amplifiers and Signal-to-Noise Ratios 180
MRH Read Amplifiers 180
Signal-to-MRH Noise Ratios 182
Magnetization Fluctuation Noise 184
Conclusions 188
Chapter 20. Colossal Magneto-Resistance and Electron Spin Tunneling Heads 189
Colossal Magneto-Resistance 189
Magnetic Tunneling Junctions 191
Chapter 21. Electrostatic Discharge Phenomena 194
Appendix Cgs-emu and MKS-SI (Rationalized) Units 197
Recommended Bibliography on Magnetic Recording 199
Index 202