MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

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172 Appendix A β changes from Heisenberg like 0.39 near T C to Ising like 0.32 further from T C . The susceptibility exponent γ = 1.17 persists to 2 T C , where it is expected to decrease to 1. The magnetization from 5 K to 100 K is well described by M = M S (1 - (T/Θ n ) n ) where n ≈ 2. The addition of a T 3/2 term is not obviously significant.
Appendix B. Magnetic Excitations and Specific Heat in SrRuO 3 Low temperature magnetic excitations can be probed not only by measurements of the magnetization but also by the heat capacity. As will be discussed below, the two measurements are related via a Maxwell relation. SrRuO 3 polycrystalline samples were prepared by repeated heating of a R u and SrCO 3 mixture at 1260°C (seciton 2.1.1). Heat capacity data were taken using the relaxation method [102] (section 3.3). Constant field data were taken on a zero field cooled sample at 0 and 8 T, and in zero field after the application of an 8 T field. In addition, data at temperatures between 4 K and 5 K were taken at several intermediate fields. Specific heat data taken in 0 T and 8 T applied magnetic field are shown in Figure B- 1. The zero field cooled and zero field remnant data are equal within experimental error. Between 3 K and 13 K both the 0 T and 8 T data appear to be well described by a straight line on this plot of c/T vs. T 2 , suggesting that the specific heat can be described by γT+βT 3 . The parameter values from fitting the data in zero field are γ = 37 mJ mol -1 K -2 and β = 0.19 mJ mol -1 K -4 . This value of β corresponds to a Debye temperature of 371 K and is in good agreement with previous zero-field measurements [176, 196], while γ is about 20% larger than that found previously. The value of γ in zero field, 37 mJ mol -1 K -2 , is 4.6 times that expected of the bare density of states given by spin resolved band structure calculations [176]. The effect of demagnetization fields should be negligible since the correction to the specific heat is approximately proportional to T 3 but only about 0.1% of the measured value of β [197, 198]. 173
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MAGNETISM AND ELECTRON TRANSPORT IN
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I certify that I have read this dis
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Preface Looking back at the many ye
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Table of Contents Abstract v Prefac
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4.2 Electronic Transport 8 5 4.2.1
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List of Figures xiii Figure 1-1 The
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Figure 5-7 Low temperature resistiv
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xvii = γT + βT 3 . The triangles
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2 Chapter 1 in themselves, but the
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4 Chapter 1 ferromagnetic metals up
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6 Chapter 1 e g t 2g e g t 2g CaMnO
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8 Chapter 1 near T C (magnetic susc
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10 Chapter 2 reactions, the rate li
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12 Chapter 2 Otherwise one has to s
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14 Chapter 2 atmosphere or vacuum.
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16 Chapter 2 a particular diffracti
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18 Chapter 2 Thus XAFS probes the l
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20 Chapter 3 relationships resistiv
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22 Chapter 3 inadequate. l ≈ a is
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24 Chapter 3 Hall effect measuremen
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26 Chapter 3 3.1.2.3 Contacts Bad c
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28 Chapter 3 3.1.2.5 Apparatus Tran
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30 Chapter 3 materials as metals or
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32 Chapter 3 overcome the barrier a
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34 Chapter 3 The dichotomy between
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36 Chapter 3 position; however, thi
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38 Chapter 3 Complex materials ofte
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40 Chapter 3 3.2.1.1 Apparatus The
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42 Chapter 3 The second-derivative
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44 Chapter 3 substances. Otherwise,
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46 Chapter 3 3.2.2.1.2 Conduction e
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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 )
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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
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4. Intrinsic Electrical Transport a
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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
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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
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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
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106 Chapter 5 χ mol (µ B /mol/T)
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108 Chapter 5 of the nonlinear M 2
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110 Chapter 5 rather than a simple
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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
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120 Chapter 6 resistivity ρ ∝ M
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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
Page 172 and 173: 154 Appendix A samples. Magnetizati
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Page 176 and 177: 158 Appendix A M 0 (µ B ) 1.0 0.8
Page 178 and 179: 160 Appendix A (T/T C - 1) γ . Fro
Page 180 and 181: 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 192 and 193: 174 Appendix B c P,H /T (mJ/mol·K
Page 194 and 195: 176 Appendix B Figure 3 at the 90%
Page 196 and 197: 178 Appendix B are vectors. Thus fo
Page 198 and 199: 180 Appendix B corrections are incl
Page 200 and 201: 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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