Magnetic Memory

Half-title......Page 3
Title......Page 5
Copyright......Page 6
Contents......Page 7
Preface......Page 11
Acknowledgments......Page 12
1.2 Magnetic forces, poles and fields......Page 13
1.3 Magnetic dipoles......Page 14
1.4 Ampère's circuital law......Page 15
1.6 Magnetic moments......Page 17
1.7 Magnetic dipole energy......Page 18
1.9 Magnetic induction......Page 19
1.10 Classical Maxwell equations of electromagnetism......Page 20
1.11 Inductance......Page 21
1.12 Equation tables......Page 22
Homework......Page 23
References......Page 24
2.1 Origin of magnetization......Page 25
2.1.2 jj coupling......Page 28
2.2 Introduction of magnetic materials......Page 29
2.2.1 Diamagnetism......Page 30
2.2.2 Paramagnetism......Page 32
2.2.3 Ferromagnetism......Page 35
Symmetry of magnetocrystalline anisotropy......Page 38
Magnetostriction......Page 39
2.2.4 Antiferromagnetism......Page 40
2.3 Ferromagnet/antiferromagnet bilayer structure......Page 42
2.3.1 Intuitive picture in exchange bias......Page 43
2.3.2 Positive exchange bias......Page 45
2.3.3 Theories of exchange bias......Page 47
2.3.4 AFM domain wall model......Page 48
2.3.5 Random field model......Page 50
2.4 Interlayer exchange coupling in ferromagnet/metal/ferromagnet multilayer......Page 51
2.4.1 Ruderman-Kittel-Kasuya-Yosida interaction......Page 53
2.4.2 Néel coupling......Page 56
2.5.1 Anisotropy energy......Page 58
2.5.3 Magnetostatic energy......Page 59
Homework......Page 60
References......Page 61
3.2 Edge poles and demagnetizing field......Page 63
3.2.1 Demagnetizing factor of elliptic-shaped film......Page 64
3.2.2 Edge curling......Page 66
3.3.1 Transition region between domains: domain wall......Page 67
3.3.2 Bloch wall and Néel wall......Page 69
3.3.3 C-state, S-state and vortex......Page 70
3.4 Magnetization behavior under an external field......Page 71
3.4.1 Magnetization rotation in a full film......Page 72
3.4.2 Magnetization rotation in a patterned film......Page 73
3.5 Magnetization switching......Page 74
3.5.1 Magnetization rotation and switching under a field in the easy-axis direction......Page 75
3.5.2 Magnetization rotation and switching under two orthogonal applied fields......Page 76
3.6 Magnetization behavior of a synthetic antiferromagnetic film stack......Page 80
Homework......Page 83
References......Page 84
4.2 Anisotropic magnetoresistance......Page 86
4.3 Giant magnetoresistance......Page 89
4.4 Tunneling magnetoresistance......Page 91
4.4.1 Giant tunneling magnetoresistance......Page 95
4.4.2 Tunneling magnetoresistance in perpendicular magnetic tunneling junction......Page 100
References......Page 101
5.1 Introduction......Page 103
5.2.1 Cross-point array......Page 105
5.2.2 1T-1MTJ cell......Page 106
5.3 Read signal......Page 107
5.3.1 Sense reference cell......Page 108
5.3.2 Sense amplifier......Page 110
5.4.1 Write-field conversion efficiency......Page 112
5.4.2 Write-line cladding......Page 113
5.5.1 Switching-energy barrier of Astroid-mode write......Page 114
5.5.3 Write soft error rate of an array of memory cells......Page 117
5.5.4 Solution to the write disturbance problem......Page 118
5.5.4.1 Segmented write......Page 119
5.5.4.2 Asymmetrical MTJ shape......Page 120
5.6.1 Toggle-mode cell......Page 121
5.6.2 Switching of SAF free layer in toggle-mode write......Page 123
5.6.3 Energy diagram of toggle operation......Page 124
5.7 Characterization method of MRAM chip write performance......Page 128
5.8 Thermally assisted field write......Page 130
5.9 Multi-transistor cells for high-speed MRAM operation......Page 131
References......Page 132
6.2 Spin polarization of free electrons in ferromagnets......Page 134
6.3 Interaction between polarized free electrons and magnetization – macroscopic model......Page 136
6.4 Spin-torque transfer in a multilayer thin-film stack......Page 138
6.5 Spin-transfer torque and switching threshold current density......Page 141
6.6 Switching characteristics and threshold in magnetic tunnel junctions......Page 143
6.6.1 Regimes of write pulse width......Page 144
6.6.2 Switching probability in the thermal regime......Page 145
Homework......Page 146
6.6.2.3 Write error rate......Page 148
6.6.2.4 Read disturb rate......Page 150
Homework......Page 151
6.6.3 Spin-torque-transfer switching under a magnetic field......Page 152
6.6.4 Magnetic back-hopping......Page 153
6.7 Reliability of tunnel barriers in MTJs......Page 155
6.8 SPICE model of MTJs and memory cells......Page 156
6.9 Memory cell operation......Page 158
6.9.1 I-V characteristics of STT memory cell during write......Page 160
6.9.2 Read and write voltage window of STT memory cell......Page 162
6.9.3 Sense signal margin......Page 163
6.9.4 Write-to-breakdown-voltage margin......Page 164
6.10 Data retention and Eb extraction method......Page 165
6.11 Thermal stability of STT memory chip......Page 166
Homework......Page 167
6.12 Write-current reduction......Page 168
6.12.1 Nanocurrent-channel film-stack structure......Page 169
6.12.3 Perpendicular MTJ......Page 171
6.13 Direct observation of magnetization reversal......Page 173
References......Page 175
7.2 MRAM market position......Page 177
7.3.2 Unbalanced MTJ flip-flop......Page 181
7.3.4 MTJ data register......Page 184
7.4 System-on-chip power reduction......Page 185
References......Page 187
Appendix A Unit conversion table for cgs and SI units......Page 188
Appendix B Dimensions of units of magnetism......Page 189
Appendix C Physical constants......Page 190
Appendix D Gaussian distribution and quantile plots......Page 191
Appendix E Weibull distribution......Page 193
Appendix F Time-dependent dielectric breakdown (TDDB) of magnetic tunnel junction devices......Page 195
Reference......Page 196
Appendix G Binomial distribution and Poisson distribution......Page 197
Appendix H Defect density and the breakdown/TMR distribution of MTJ devices......Page 199
Appendix I Fe, Ni and Co material parameters......Page 201
Appendix J Soft error, hard fail and design margin......Page 202
Homework......Page 204
Index......Page 205