Contents 1 Introduction 1 References 3 2 Electron Shell Structure of Free Atoms and Valence Electrons in Crystals 5 2.1 Electron Shell Structure of Free Atoms 5 2.2 A Simple Introduction to Classical Crystal Binding Theory for Typical Magnetic Materials 6 2.3 Effective Radii of Ions in Crystals 8 2.4 Electron Binding Energy Originating from Ions in Crystals 9 References 11 3 A Simple Introduction to Basic Knowledge of Magnetic Materials 13 3.1 Classification of Matter Based on Magnetic Properties 13 3.2 Magnetic Domain and Domain Wall 16 3.3 Basic Parameters of Magnetic Materials 18 3.4 Magnetic Ordering Models in Conventional Ferromagnetism 21 References 24 4 Difficulties Faced by Conventional Magnetic Ordering Models 25 4.1 Disputes Over the Cation Distributions in Mn and Cr Spinel Ferrites 25 4.1.1 Normal, Inverse, and Mixed Spinel Structure 25 4.1.2 Magnetic Moments of 3d Transition Metal Ions 27 4.1.3 Magnetic Ordering of CrFe204 and MnFe204 27 4.2 Difficulties in Describing the Observed Magnetic Moments of Perovskite Manganites 31 4.3 Relationship Between Magnetic Moment and Resistivity in Typical Magnetic Metals 38 4.4 Puzzle for the Origin of Magnetic Ordering Energy 38 References 39 5 02p Itinerant Electron Model for Magnetic Oxides 43 5.1 A Simple Introduction to Early Investigations of Ionicity 43 5.2 Study of the Ionicity of Spinel Ferrites 45 5.2.1 Quantum-Mechanical Potential Barrier Model Used to Estimate Cation Distributions 46 5.2.2 Study of the Ionicity of Group II-VI Compounds Using the Quantum-Mechanical Potential Barrier Model 47 5.2.3 Study of Ionicity of Spinel Ferrite Fe3o4 48 5.2.4 Estimation of the Ionicity of Spinel Ferrites M3O4 Using the Quantum- Mechanical Potential Barrier Model 50 5.3 Experimental Studies of O 2p Holes in Oxides 51 5.3.1 O 2p Hole Studies Using Electron Energy Loss Spectroscopy 52 5.3.2 Several Other Experimental Investigations for O 2p Holes 54 5.4 Study of Negative Monovalent Oxygen Ions Using X-Ray Photoelectron Spectra 54 5.4.1 Study of Ionicity of BaTiC>3 and Several Monoxides Using O Is XPS 55 5.4.2 Effect of Argon Ion Etching on the O Is Photoelectron Spectra of SrTio3 60 5.5 O 2p Itinerant Electron Model for Magnetic Oxides (IEO Model) 70 5.6 Relationship Between the IEO Model and the Conventional Models 75 References 79 6 Magnetic Ordering of Typical Spinel Ferrites 81 6.1 Method Fitting Magnetic Moments of Typical Spinel Ferrites 81 6.1.1 X-ray Diffraction Analysis 82 6.1.2 Magnetic Property Measurements 84 6.1.3 Primary Factors that Affect Cation Distributions 85 6.1.4 Fitting the Magnetic Moments of the Samples 88 6.1.5 Discussion on Cation Distributions 91 6.2 Cation Distribution Characteristics in Typical Spinel Ferrites 94 References 100 7 Experimental Evidences of the IEO Model Obtained from Spinel Ferrites 101 7.1 Additional Antiferromagnetic Phase in Ti-Doped Spinel Ferrites 101 7.1.1 X-ray Diffraction Spectra of the Samples 102 7.1.2 X-ray Energy Dispersive Spectra of the Samples 104 7.1.3 Magnetic Measurements and Analysis of the Results 106 7.1.4 Cation Distributions of the Three Series of Ti-Doped Samples 108 7.1.5 Magnetic Ordering of Spinel Ferrites TicM1_xFe204 (M = Co, Mn) 115 7.2 Amplification of Spinel Ferrite Magnetic Moment Due to Cu Substituting for Cr 116 7.2.1 X-ray Energy Dispersive Spectrum Analysis 116 7.2.2 X-ray Diffraction Analysis 117 7.2.3 Magnetic Measurement and Magnetic Moment Fitting Results 118 7.3 Unusual Infrared Spectra of Cr Ferrite 122 7.3.1 Infrared Spectra of Spinel Ferrites M￥q2Oa (M=Fe, Co, Ni, Cu, Cr) 123 7.3.2 Dependency of the Peak Position V2 on the Magnetic Moment (/Xm2) of Divalent M Cations in MFe2O4(M= Fe, Co, Ni, Cu, Cr) 125 7.3.3 Infrared Spectra of and CoCrxFe2-x04 126 References 126 8 Spinel Ferrites with Canted Magnetic Coupling 129 8.1 Spinel Ferrites with Fe Ratio Being Less Than 2.0 Per Molecule 129 8.2 Spinel Ferrites Containing Nonmagnetic Cations 132 8.2.1 Disputation of Nonmagnetic Cation Distribution 133 8.2.2 Fitting Sample Magnetic Moments 136 8.2.3 Discussion on Cation Distributions 137 References 145 9 Magnetic Ordering and Electrical Transport of Perovskite Manganites 147 9.1 Ferromagnetic and Antiferromagnetic Coupling in Typical Perovskite Manganites 147 9.1.1 Crystal Structure and Magnetic Measurement Results of Lai-xSrxMnOs Polycrystalline Powder Samples 147 9.1.2 Study of Valence and Ionicity of Lai-xSrxMn03 150 9.1.3 Fitting of the Curve of the Magnetic Moment Versus Sr Ratio for Lai-xSrxMn03 152 9.2 Spin-Dependent and Spin-Independent Electrical Transport of Perovskite Manganites 155 9.2.1 A Model with Two Channels of Electrical Transport for ABO3 Perovskite Manganites 156 9.2.2 Fitting the Curves of Resistivity Versus Test Temperature of Single-Crystal Lai-^Sr^MnOs 157 9.2.3 Fitting the Curves of Resistivity Versus Test Temperature of Lao‘6oSro.4oFexMni_x03 Polycrystalline Samples 158 9.2.4 Discussion on Factors Affecting Electrical Transport Property 160 9.3 Experimental Evidence on the Canting Angle Magnetic Structure in Perovskite Manganites 166 9.3.1 Analyses for the Crystal Structure of the Samples 167 9.3.2 Magnetic Measurement Results 169 9.3.3 Measurement Results of Electrical Transport Property 174 9.3.4 Fitting of Sample Magnetic Moment Using the IEO Model 179 9.3.5 Effects of Thermal Excitation, Lattice Scattering, and Spin-Dependent Scattering on the Transition Probability of Itinerant Electrons 180 9.3.6 Effect of Canted Ferromagnetic Coupling on Magnetoresistance 182 9.4 Magnetic Coupling Between the Two Sublattices in Perovskite Praseodymium Manganites 184 9.5 Substituting for Mn in Perovskite Praseodymium Manganites 186 9.5.1 Fitting of the Sample Magnetic Moment as the Function of Doped Level 187 9.5.2 Influence of Canted Magnetic Structure on the Magnetoresistance 189 9.6 Experimental Evidence for Antiferromagnetic Coupling Between Divalent and Trivalent Mn Ions in Perovskite Manganites 190 9.6.1 Preparation of the Samples 190 9.6.2 Crystal Structure and Crystal Lattice Constants of the Samples 191 9.6.3 Magnetic Measurement Results 191 9.6.4 Discussion on the Magnetic Structures of the Samples 193 References 200 10 Antiferromagnetic Ordering in Oxides with Sodium Chlonde Structure 203 10.1 Characteristics of Antiferromagnetic Oxides with Sodium Chloride Structure 203 10.2 Difference Between Magnetic Structures of Manganese Monoxide and Lanthanum Manganite 205 References 206 11 Itinerant Electron Model for Magnetic Metals 207 11.1 Experimental and Theoretical Studies for Atomic Magnetic Moments in Metals 207 11.2 Itinerant Electron Model for Magnetic Metals (IEM Model) 208 References 211 12 Study on the Origin of Magnetic Ordering Energy for Magnetic Materials 213 12.1 Weiss Molecular Field 213 12.2 Thermal Expansion of Perovskite Manganites Near the Curie Temperature 215 12.3 Weiss Electron Pair (WEP) Model for Origin of Magnetic Ordering Energy 215 12.4 Explanation for the Curie Temperature Difference of Typical Magnetic Materials 221 12.5 Explanation for Cu Ratio Dependence of Resistivity and Curie Temperature for NiCu Alloys 222 12.5.1 Free and 3d Electron Ratios in NiCu Alloys 222 12.5.2 Electrical Transport Model with FE and IE Channels 223 12.5.3 An Explanation of the Curie Temperature Using the WEP Model 226 References 229 13 Prospects and Challenges for Future Work 231 13.1 Other Factors Affecting Magnetic Ordering Energy 231 13.2 Magnetic Ordering Energy in DFT Calculations 233 13.3 Applications of the IEO and IEM Models 233 References 234 Appendix A Electron Structure and Ionization Energies of Free Atoms 235 Appendix B Effective Ion Radii Reported by Shannon 239 Appendix C Symbol Notes 253
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