Magnetic Materials
Magnetic materials consist of a wide variety of metals and oxides. Their effective properties are given by a combination of two property categories: intrinsic properties which are the atomic moment per atom p at, Curie temperature T c, magnetocrystalline
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4.3.1 Basic Magnetic Properties.................... 4.3.1.1 Atomic Moment ...................... 4.3.1.2 Magnetocrystalline Anisotropy .. 4.3.1.3 Magnetostriction .....................
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4.3.2 Soft Magnetic Alloys............................ 4.3.2.1 Low Carbon Steels ................... 4.3.2.2 Fe-based Sintered and Composite Soft Magnetic Materials................................ 4.3.2.3 Iron–Silicon Alloys................... 4.3.2.4 Nickel–Iron-Based Alloys ......... 4.3.2.5 Iron–Cobalt Alloys ................... 4.3.2.6 Amorphous Metallic Alloys........ 4.3.2.7 Nanocrystalline Soft Magnetic Alloys .................................... 4.3.2.8 Invar and Elinvar Alloys ...........
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4.3.3 Hard Magnetic Alloys .......................... 4.3.3.1 Fe–Co–Cr ............................... 4.3.3.2 Fe–Co–V ................................ 4.3.3.3 Fe–Ni–Al–Co, Alnico ................ 4.3.3.4 Fe–Nd–B................................ 4.3.3.5 Co–Sm ................................... 4.3.3.6 Mn–Al–C ................................
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4.3.4 Magnetic Oxides ................................. 811 4.3.4.1 Soft Magnetic Ferrites .............. 811 4.3.4.2 Hard Magnetic Ferrites ............. 813 References .................................................. 814
4.3.1 Basic Magnetic Properties Basic magnetic properties of metallic systems and materials are treated by Gignoux in [3.1]. Extensive data on magnetic properties of metals can be found in [3.2]. Magnetic properties of ferrites are treated by Guillot in [3.3]. Extensive data on magnetic and other properties of oxides and related compounds can be found in [3.4] and [3.5].
4.3.1.1 Atomic Moment The suitability of a metal or oxide to be used as a magnetic material is determined by its mean atomic
moment ( pat ). For metals the Bethe–Slater–Pauling curves, Fig. 4.3-1, indicate how pat depends on the average number (n) of 3d and 4s electrons per atom, and on the crystal structure, i. e., face-centered cubic (fcc) or body-centered cubic (bcc) structure. Alloys based on Fe, Co, and Ni are most suitable from this point of view, corresponding to their actual use. The characteristic temperature dependence of the spontaneous magnetization Is (T ), shown for Fe in Fig. 4.3-2, the Curie temperature Tc and the spontaneous magnetization at room temperature Is (see Table 4.3-1), are the ensuing properties.
Part 4 3
Magnetic materials consist of a wide variety of metals and oxides. Their effective properties are given by a combination of two property categories: intrinsic properties which are the atomic moment per atom pat , Curie temperature Tc , magnetocrystalline anisotropy coefficients Ki , and magnetostriction coefficients λi ; and extrinsic properties which are essentially their coercivity Hc and their magnetisation M or magnetic Induction J as a function of the applied magnetic field H. Moreover, the effective properties are depending decisively on the microstructural features, texture and, in most ca
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