MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

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70 Chapter 3 Magnetization (µ B ) 0.01645 0.01640 0.01635 0.01630 0.01625 0.01620 Magnetization Creep 100 1000 Time (s) 10000 Figure 3-15 Time dependent magnetization of SrRuO 3 pellet at 5 K. The field was increased from 0 to 100 Gauss. The magnetization follows a Log(time) dependence. ferromagnet. This leads to a negative paramagnetic Curie temperature Θ P ≈ -T N , where the susceptibility above T N is given by χ mol 2 2 NAµ B gJJ ( + 1) = 3k T − Θ . B P Below the ordering temperature T N , M vs. H is still linear with no H = 0 magnetization, but the susceptibility depends on the orientation of the magnetic field with respect to that of the magnetic moments [56]. For example, Figure 3-16 shows the susceptibility of platinum containing “CaRuO 3 ” crystals, or CaRu/PtO 3 described in section 2.1.2.1. If the magnetic field is applied parallel to the ordered moments, the applied torque (µ × H) is small so the susceptibility decreases to zero. The CaRu/PtO 3 crystal when oriented with the 2-fold symmetric axis parallel to H shows such a susceptibility. When the field is perpendicular to the ordered moments, the torque is maximized providing a large, constant susceptibility in the ordered
χ (emu/g/G) 4.0 10 -5 3.5 10 -5 3.0 10 -5 2.5 10 -5 2.0 10 -5 1.5 10 -5 1.0 10 -5 Electronic and Magnetic Measurements 71 5.0 10 -6 0 50 100 150 200 250 300 350 400 Temperature (K) state. This is seen in the crystals oriented with a 3-fold symmetric axis parallel to H. Without Pt, CaRuO 3 has an antiferromagnetic like susceptibility (1/(T + Θ P )) above 50K (Θ P ≈ -210K p eff ≈ 9.75 or S ≈ 1.14) but does not become antiferromagnetic. Instead, it remains paramagnetic but with a stronger temperature dependence ≈ 1/T (Figure 3-16). From 2 K to 20 K the susceptibility fits well to (1/(T + Θ P )) with an antiferromagnetic slope (Θ P = -73K p eff = 4.17 or S = 0.64). CaRuO 3 and Pt Containing CaRuO 3 Crystal CaRuO 3 3-fold axis crystal 2-fold axis crystal Figure 3-16 Magnetic susceptibility of a Pt containing “CaRuO 3 ” crystal. The crystal was aligned with its 2-fold symmetric axis parallel to the applied field has a susceptibility characteristic of antiferromagnetic moments aligning parallel to the field, while the 3-fold axis appears to have moments perpendicular to the field. 3.2.2.4 Ferrimagnetism If the sublattices of different moment orientation do not exactly cancel, there is then a small ferromagnetic moment in the ordered state, that behaves
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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
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,
Page 64 and 65: 46 Chapter 3 3.2.2.1.2 Conduction e
Page 66 and 67: 48 Chapter 3 Susceptibility (emu/G
Page 68 and 69: 50 Chapter 3 H/M (T/μ B ) 80 70 60
Page 70 and 71: 52 Chapter 3 Magnetization (μ B )
Page 72 and 73: 54 Chapter 3 is called the Stoner c
Page 74 and 75: 56 Chapter 3 Energy Magnetic Excita
Page 76 and 77: 58 Chapter 3 moments [84]. Thus, a
Page 78 and 79: 60 Chapter 3 Arrott plot), will the
Page 80 and 81: 62 Chapter 3 Curie temperature, the
Page 82 and 83: 64 Chapter 3 The energy ω of a spi
Page 84 and 85: 66 Chapter 3 3.2.2.2.9 Irreversibil
Page 86 and 87: 68 Chapter 3 ferromagnet will also
Page 90 and 91: 72 Chapter 3 with temperature and f
Page 92 and 93: 74 Chapter 3 by Mn +4 2 (S = 3/2).
Page 94 and 95: 76 Chapter 3 ferromagnet. Instead,
Page 96 and 97: 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
Page 102 and 103: 84 Chapter 4 M/M 0 1.00 0.96 0.92 0
Page 104 and 105: 86 Chapter 4 Resistivity (10 -3 Ω
Page 106 and 107: 88 Chapter 4 dependence of R 2 is s
Page 108 and 109: 90 Chapter 4 magnetoresistance obse
Page 110 and 111: 92 Chapter 4 4. 2. 2 High Temperatu
Page 112 and 113: 94 Chapter 4 measurements (Figure 4
Page 114 and 115: 96 Chapter 4 somewhat too large com
Page 116 and 117: 98 Chapter 4 Magnetization 8 6 4 2
Page 118 and 119: 100 Chapter 4 above room temperatur
Page 120 and 121: 102 Chapter 5 5.1 Ferrimagnetism Th
Page 122 and 123: 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
Page 132 and 133: 114 Chapter 5 A high, temperature i
Page 134 and 135: 116 Chapter 5 5. 3. 1 Relationship
Page 136 and 137: 6. Magnetoconductivity in La 0.67Ca
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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
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134 Chapter 7 spin-relaxation measu
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136 Chapter 7 1/χ (10kOe/µ B ) 5
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138 Chapter 7 γ < 1. Also, at a co
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140 Chapter 7 ∆R/R (%) 10 0 -10 -
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142 Chapter 7 (Figure 7-6), in so f
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144 Chapter 7 The related form ρ
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146 Chapter 7 σ H (10 -5 mΩcm -1
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148 Chapter 7 σ E exp[M 0 (T)/M E
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150 Chapter 7 σ = σ E exp[M(H,T)/
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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
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164 Appendix A 1/χ 0 (emu -1 mol G
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166 Appendix A T 3/2 Coefficient (1
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168 Appendix A magnetization with t
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170 Appendix A excitations for T <
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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%
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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.
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184 References [40] G. J. Snyder an
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186 References [80] E. C. Stoner, P
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188 References [115] M. F. Hundley,
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190 References [151] S. J. L. Billi
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192 References [187] L. Klein, (unp
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MAGNETISM ELECTRON TRANSPORT MAGNETORESISTIVE LANTHANUM CALCIUM MANGANITE

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