1 Organic, inorganic and composite ferroelectrics .............. 1
1.1 Introduction ............................................ 1
1.2 Organic and inorganic ferroelectrics .................... 2
1.3 Composite ferroelectrics ................................ 7
1.4 Displacive and order-disorder-type phase transitions .... 9
1.5 Quantum paraelectrics and incipient displacive
ferroelectrics ......................................... 12
1.6 Disorder in displacive ferroelectrics .................. 15
1.7 New developments in KH2PO4-type order-disorder
ferroelectrics ......................................... 19
2 Incommensurate systems ...................................... 23
2.1 One-dimensionally modulated incommensurate systems ..... 23
2.1.1 Commensurate (C) and incommensurate (I)
systems ......................................... 23
2.1.2 Phase transitions to incommensurate phases ...... 24
2.1.3 The observation of structurally incommensurate
systems ......................................... 27
2.1.4 The theoretical side: Solitons, the Devil's
staircase and phasons ........................... 28
2.1.5 Dielectric properties ........................... 32
2.1.5.1 Polarization in incommensurate
structures ............................. 32
2.1.5.2 The paraphase and the commensurate
phase .................................. 33
2.1.5.3 Proper ferroelectrics .................. 33
2.1.5.4 Improper ferroelectrics ................ 34
2.1.5.5 The incommensurate phase ............... 35
2.1.5.6 Proper ferroelectrics .................. 35
2.1.5.7 Improper ferroelectrics ................ 36
2.1.5.8 The static dielectric constant ......... 36
2.1.6 Neutron and X-ray scattering .................... 38
2.1.6.1 Probing the displacements in
incommensurate, structures ............. 38
2.1.6.2 Elastic scattering ..................... 39
2.1.7 Magnetic resonance lineshapes in incommensurate
systems ......................................... 43
2.1.7.1 Number of resonance lines and
frequency distribution ................. 43
2.1.8 The 'plane-wave' limit: One-dimensional
modulation (m = 1) .............................. 45
2.1.8.1 Linear case ............................ 46
2.1.8.2 Quadratic case ......................... 46
2.1.8.3 Linear and quadratic terms ............. 47
2.1.9 The'phase soliton'limit ......................... 47
2.1.9.1 Soliton density and Landau theory
(Fig. 2.15) ............................ 47
2.1.9.2 The NMR lineshape in the multisoliton
limit .................................. 51
2.1.10 Phason and amplitudon excitations ............... 52
2.1.10.1 Dispersion relations ................... 52
2.2 Multidimensionally modulated incommensurate systems .... 55
2.2.1 NMR and multidimensional modulation ............. 57
2.2.2 2-q modulation .................................. 59
2.2.3 Dispersion relations in incommensurate systems
and T1-1 ........................................ 61
2.2.4 3-q modulation .................................. 62
2.2.5 The determination of the relative phases of
the modulation waves ............................ 63
2.2.6 Local and non-local case ........................ 64
2.2.7 Multisoliton lattice limit ...................... 67
2.2.8 Systems with a 6-component order parameter ...... 70
2.2.8.1 75As NQR in proustite: The non-planar
3-q case ............................... 70
2.3 Conclusions ............................................ 78
3 Ferroelectric liquid crystals ............................... 79
3.1 Modulated ferroelectric liquid crystals ................ 81
3.2 Excitations in ferroelectric liquid crystals: The
Goldstone mode, the amplitudon mode and the soft
mode ................................................... 84
3.3 The magnetic-field-induced Lifshitz point .............. 89
3.4 The electric-field-induced Lifshitz point .............. 91
3.5 Freely suspended ferroelectric smectic thin films ...... 93
4 Dipolar glasses ............................................. 95
4.1 Introduction ........................................... 95
4.2 Local structure determination and local polarization
distribution function .................................. 96
4.3 Dielectric properties .................................. 99
4.4 NMR in homogeneous ferroelectrics and anti-
ferroelectrics in the fast-motion regime .............. 100
4.4.1 Deuteron NMR and relaxation .................... 101
4.4.2 Oxygen-17-proton nuclear quadrupole double
resonance ...................................... 103
4.4.3 Proton chemical-shift tensors .................. 108
4.4.4 Phosphorus-31 chemical-shift tensors ........... 108
4.4.5 Arsenic-75 quadrupolar coupling ................ 110
4.5 NMR in proton and deuteron glasses .................... 112
4.5.1 Determination of the Edwards-Anderson order
parameter зea in the fast-motion limit ......... 112
4.5.2 Determination of the Edwards-Anderson glass
order parameter q in the slow-motion limit ..... 115
4.6 NMR determination of order parameters in
inhomogeneous ferroelectrics .......................... 117
4.7 Theory of dipolar glasses: The random-bond-random-
field Ising model ..................................... 118
4.8 Conclusions ........................................... 120
5 Magnetoelectric ferroelectrics ............................. 121
5.1 Introduction .......................................... 121
5.2 The quadratic ME effect in Pb (Fe1/2Nb1/2)O3 .......... 126
5.3 Ferroelectric polarization reversal by electric and
magnetic fields ....................................... 128
5.4 The modified Vogel-Fulcher relation in external
fields and the polar nanocluster size ................. 129
5.5 Theory of bi-relaxors ................................. 131
5.5.1 Spherical model of bi-relaxors ................. 133
5.5.2 Static dielectric properties under constant
magnetic field ................................. 135
5.5.3 Dynamic dielectric response .................... 137
5.5.4 Relaxation of dielectric polarization in
magnetic field ................................. 139
6 Relaxor ferroelectrics ..................................... 144
6.1 Introduction .......................................... 144
6.2 Specific heat of relaxors ............................. 148
6.3 The rigid spherical random-bond-random-field (SRBRF)
model ................................................. 149
6.4 Pseudospin phonon coupling ............................ 150
6.5 The SRBRF phase diagram ............................... 151
6.6 Linear and non-linear dielectric response ............. 153
6.6.1 The difference between relaxors and
ferroelectrics ................................. 155
6.7 Ferroelectrics in random fields ....................... 159
6.8 PbMg1/3Nb2/3O3(PMN) and related perovskite relaxors:
Phase diagrams, neutron scattering, Raman spectra
and heat conductivity ................................. 159
6.9 Effect of pressure .................................... 163
6.10 NMR lineshapes and relaxation times in relaxor PMN:
Evidence of polar clusters ............................ 165
6.11 Electric-field-induced critical end points in PMN-PT
relaxors and giant йlectrostriction ................... 170
6.11.1 Landau theory .................................. 173
6.11.2 Experimental data .............................. 176
6.12 Critical end points up to 8th-order terms ............. 183
7 Ferroelectric polymers ..................................... 187
7.1 2D ferroelectricity ................................... 191
7.2 Spherical model of relaxor polymers ................... 191
7.2.1 Polar nanoregions .............................. 191
7.2.2 Free energy .................................... 193
7.2.3 Order parameters ............................... 194
7.3 Dielectric susceptibility ............................. 195
7.3.1 Longitudinal and transverse susceptibilities ... 195
7.3.2 Spontaneous polarization ....................... 198
7.3.3 Non-linear susceptibility ...................... 199
7.4 Electrostriction ...................................... 201
8 Electrocaloric effect in ferroelectrics and ferroelectric
thin films ................................................. 203
9 Ferroelectric thin films ................................... 215
9.1 The Tilley-Žekš model ................................. 219
9.1.1 The positive-positive case ..................... 224
9.1.2 The negative-negative case ..................... 225
9.1.3 The mixed case ................................. 225
9.2 Misfit-strain-induced magnetoelectric coupling in
thin films ............................................ 226
10 Nanoferroelectrics ......................................... 230
10.1 Surface piezoelectric, piezomagnetic and ME tensors ... 230
10.2 Size-induced ferroelectricity in non-ferroelectric
insulators ............................................ 235
10.3 Spontaneous flexoelectric effect in nanoferroics ...... 239
10.3.1 Basic equations for the flexoeffect in
ferroic nanoparticles .......................... 240
10.3.2 Thin pills ..................................... 241
10.3.3 Nanowires ...................................... 241
10.4 Ferroelectric vortex states: Phase transitions in
zero-dimensional nanoferroelectrics ................... 243
Appendix ...................................................... 247
References .................................................... 251
Subject index ................................................. 269
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