MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

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viii inspiration behind the irreversibility line plot in section 3.2.2.2.9. Thanks also to Khiem, Steve, Daniel & Jenny, Laurent and the rest of the curry club for great conversations at lunch. Much of this work was done in collaboration with Hewlett-Packard in Palo Alto. The MOCVD films of the manganites were made by Ron Hiskes and Steve DiCarolis. The XAFS studies in Chapter 5 were performed at the Stanford Linear Accelerator by Corwin Booth and Bud Bridges from U. C. Santa Cruz. This work could not have been completed without the support of friends, housemates, parents but particularly Sossina Ñ thank you very much. Funding for this research was generously provided by The Fanny and John Hertz Foundation, the Air Force Office of Scientific Research, and the Stanford Center for Materials Research under the NSF-MRL program
Table of Contents Abstract v Preface vii Table of Contents i x List of Figures xiii List of Tables xvii 1. INTRODUCTION 1 1.1 Motivation 2 1.2 AMnO 3 1.3 Double Exchange 5 2. MATERIALS SYNTHESIS AND CHARACTERIZATION 9 2.1 Sample Preparation 9 2.1.1 Bulk Polycrystalline Samples 9 2.1.2 Single Crystals 10 2.1.2.1 Flux Growth 11 2.1.2.2 Float Zone 12 2.1.2.3 Thin Films 13 2.1.3 Reactive Samples 13 2.2 Characterization 1 4 2.2.1 Elemental Analysis 14 2.2.2 Structural Analysis 14 2.2.2.1 Neutron diffraction 15 2.2.2.2 X-ray diffraction 15 2.2.2.2.1 Powder X-ray diffraction 16 2.2.2.2.2 Single crystal and films 17 2.2.2.3 X-ray Absorption Fine Structure 17 3. <strong>ELECTRON</strong>IC AND MAGNETIC MEASUREMENTS 1 9 3.1 Transport Properties 1 9 3.1.1.1 Ohm’s Law 19 3.1.1.2 Magnetoresistance 20 3.1.1.3 Drift velocity, mobility, relaxation time and mean free path 21 3.1.1.4 Hall effects 22 3.1.2 Measurement 22 3.1.2.1 Linearity 23 3.1.2.2 Geometry 24 ix 3
Page 1 and 2: MAGNETISM AND ELECTRON TRANSPORT IN
Page 3: I certify that I have read this dis
Page 7: Preface Looking back at the many ye
Page 11 and 12: 4.2 Electronic Transport 8 5 4.2.1
Page 13 and 14: List of Figures xiii Figure 1-1 The
Page 15 and 16: Figure 5-7 Low temperature resistiv
Page 17: xvii = γT + βT 3 . The triangles
Page 20 and 21: 2 Chapter 1 in themselves, but the
Page 22 and 23: 4 Chapter 1 ferromagnetic metals up
Page 24 and 25: 6 Chapter 1 e g t 2g e g t 2g CaMnO
Page 26 and 27: 8 Chapter 1 near T C (magnetic susc
Page 28 and 29: 10 Chapter 2 reactions, the rate li
Page 30 and 31: 12 Chapter 2 Otherwise one has to s
Page 32 and 33: 14 Chapter 2 atmosphere or vacuum.
Page 34 and 35: 16 Chapter 2 a particular diffracti
Page 36 and 37: 18 Chapter 2 Thus XAFS probes the l
Page 38 and 39: 20 Chapter 3 relationships resistiv
Page 40 and 41: 22 Chapter 3 inadequate. l ≈ a is
Page 42 and 43: 24 Chapter 3 Hall effect measuremen
Page 44 and 45: 26 Chapter 3 3.1.2.3 Contacts Bad c
Page 46 and 47: 28 Chapter 3 3.1.2.5 Apparatus Tran
Page 48 and 49: 30 Chapter 3 materials as metals or
Page 50 and 51: 32 Chapter 3 overcome the barrier a
Page 52 and 53: 34 Chapter 3 The dichotomy between
Page 54 and 55: 36 Chapter 3 position; however, thi
Page 56 and 57: 38 Chapter 3 Complex materials ofte
Page 58 and 59:
40 Chapter 3 3.2.1.1 Apparatus The
Page 60 and 61:
42 Chapter 3 The second-derivative
Page 62 and 63:
44 Chapter 3 substances. Otherwise,
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46 Chapter 3 3.2.2.1.2 Conduction e
Page 66 and 67:
48 Chapter 3 Susceptibility (emu/G
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50 Chapter 3 H/M (T/μ B ) 80 70 60
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52 Chapter 3 Magnetization (μ B )
Page 72 and 73:
54 Chapter 3 is called the Stoner c
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56 Chapter 3 Energy Magnetic Excita
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58 Chapter 3 moments [84]. Thus, a
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60 Chapter 3 Arrott plot), will the
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62 Chapter 3 Curie temperature, the
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64 Chapter 3 The energy ω of a spi
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66 Chapter 3 3.2.2.2.9 Irreversibil
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68 Chapter 3 ferromagnet will also
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70 Chapter 3 Magnetization (µ B )
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72 Chapter 3 with temperature and f
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74 Chapter 3 by Mn +4 2 (S = 3/2).
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76 Chapter 3 ferromagnet. Instead,
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78 Chapter 3 3.3.1.1 Apparatus The
Page 98 and 99:
4. Intrinsic Electrical Transport a
Page 100 and 101:
82 Chapter 4 M/M 0 1.0 0.8 0.6 0.4
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84 Chapter 4 M/M 0 1.00 0.96 0.92 0
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86 Chapter 4 Resistivity (10 -3 Ω
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88 Chapter 4 dependence of R 2 is s
Page 108 and 109:
90 Chapter 4 magnetoresistance obse
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92 Chapter 4 4. 2. 2 High Temperatu
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94 Chapter 4 measurements (Figure 4
Page 114 and 115:
96 Chapter 4 somewhat too large com
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98 Chapter 4 Magnetization 8 6 4 2
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100 Chapter 4 above room temperatur
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102 Chapter 5 5.1 Ferrimagnetism Th
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104 Chapter 5 calculation predicts
Page 124 and 125:
106 Chapter 5 χ mol (µ B /mol/T)
Page 126 and 127:
108 Chapter 5 of the nonlinear M 2
Page 128 and 129:
110 Chapter 5 rather than a simple
Page 130 and 131:
112 Chapter 5 ln(ρ /Ω cm) 24 22
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114 Chapter 5 A high, temperature i
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116 Chapter 5 5. 3. 1 Relationship
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6. Magnetoconductivity in La 0.67Ca
Page 138 and 139:
120 Chapter 6 resistivity ρ ∝ M
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122 Chapter 6 The Hall effects are
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124 Chapter 6 ∆R/R (%) 1 0 -1 -2
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126 Chapter 6 R(H)-R(-H) (µΩ cm)
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7. Critical Transport and Magnetiza
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130 Chapter 7 2 ) M 2 (µ B The foc
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132 Chapter 7 for T > T C . The reg
Page 152 and 153:
134 Chapter 7 spin-relaxation measu
Page 154 and 155:
136 Chapter 7 1/χ (10kOe/µ B ) 5
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138 Chapter 7 γ < 1. Also, at a co
Page 158 and 159:
140 Chapter 7 ∆R/R (%) 10 0 -10 -
Page 160 and 161:
142 Chapter 7 (Figure 7-6), in so f
Page 162 and 163:
144 Chapter 7 The related form ρ
Page 164 and 165:
146 Chapter 7 σ H (10 -5 mΩcm -1
Page 166 and 167:
148 Chapter 7 σ E exp[M 0 (T)/M E
Page 168 and 169:
150 Chapter 7 σ = σ E exp[M(H,T)/
Page 170 and 171:
Appendix A. Critical Behavior and A
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154 Appendix A samples. Magnetizati
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156 Appendix A while the pellet dis
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158 Appendix A M 0 (µ B ) 1.0 0.8
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160 Appendix A (T/T C - 1) γ . Fro
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162 Appendix A provides highly reve
Page 182 and 183:
164 Appendix A 1/χ 0 (emu -1 mol G
Page 184 and 185:
166 Appendix A T 3/2 Coefficient (1
Page 186 and 187:
168 Appendix A magnetization with t
Page 188 and 189:
170 Appendix A excitations for T <
Page 190 and 191:
172 Appendix A β changes from Heis
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174 Appendix B c P,H /T (mJ/mol·K
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176 Appendix B Figure 3 at the 90%
Page 196 and 197:
178 Appendix B are vectors. Thus fo
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180 Appendix B corrections are incl
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References [1] G. H. Jonker and H.
Page 202 and 203:
184 References [40] G. J. Snyder an
Page 204 and 205:
186 References [80] E. C. Stoner, P
Page 206 and 207:
188 References [115] M. F. Hundley,
Page 208 and 209:
190 References [151] S. J. L. Billi
Page 210:
192 References [187] L. Klein, (unp
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MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

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