This chapter contains sections titled: Introduction Domain Wall Structure Domain Wall Observation Magnetostatic Energy and Domain Structure Single-Domain Particles Micromagnetics Domain Wall Motion Hindrances to Wall Motion (Inclusions) Residual Stress Hindrances to Wall Motion (Microstress) Hindrances to Wall Motion (General) Magnetization by Rotation Magnetization in Low Fields Magnetization in High Fields Shapes of Hysteresis Loops Effect of Plastic Deformation (Cold Work) Problems

This chapter contains sections titled: Introduction Magnetic Moments of Electrons Magnetic Moments of Atoms Theory of Diamagnetism Diamagnetic Substances Classical Theory of Paramagnetism Quantum Theory of Paramagnetism Paramagnetic Substances Problems

Introduction to Magnetic Materials, 2nd Edition covers the basics of magnetic quantities, magnetic devices, and materials used in practice. While retaining much of the original, this revision now covers SQUID and alternating gradient magnetometers, magnetic force microscope, Kerr effect, amorphous alloys, rare-earth magnets, SI Units alongside cgs units, and other up-to-date topics. In addition, the authors have added an entirely new chapter on information materials. The text presents materials at the practical rather than theoretical level, allowing for a physical, quantitative, measurement-based understanding of magnetism among readers, be they professional engineers or graduate-level students.

This chapter contains sections titled: Introduction Single-Domain vs Multi-Domain Behavior Coercivity of Fine Particles Magnetization Reversal by Spin Rotation Magnetization Reversal by Wall Motion Superparamagnetism in Fine Particles Superparamagnetism in Alloys Exchange Anisotropy Preparation and Structure of Thin Films Induced Anisotropy in Films Domain Walls in Films Domains in Films Problems

Since the measurement of residual stress by X-ray diffraction techniques is dependent on the difference in angle of a diffraction peak maximum when the sample is examined consecutively with its surface at two different angles to the diffracting planes, it is important that these diffraction angles be obtained precisely, preferably with an accuracy of ± 0.01 deg. 2θ. Similar accuracy is desired in precise lattice parameter determination. In such measurements, it is imperative that the diffractometer be well-aligned. It is in the context of diffractometer alignment with the aid of a silicon powder standard free of residual stress that the diffraction peak analysis techniques described here have been developed, preparatory to residual stress determinations.

Some kinds of plastic deformation leave a residual pseudo-macrostress in the material. The existence of this stress in certain specimens introduces errors into the standard x-ray measurement of residual macrostress, namely, in specimens that have been stretched, compressed, bent, rolled, or drawn.No error is involved in x-ray measurements on peened, ground, or machined surfaces, or in specimens where the source of the stress is remote from the surface examined.The x-ray and magnetic evidence for pseudo-macrostress is reviewed.

A variety of faulted polytypic forms which depend on thermal history and probably on chemical composition have been observed for Dy2Co17. For a sample having predominantly a mixture of 4H and 6H intergrowths, a ferrimagnetic domain wall has been observed in TEM which moves easily with changes of field and whose orientation depends on local foil thickness. For a Bloch wall in this easy‐basal‐plane intermetallic one expects the wall to be parallel to the basal plane. In the situation observed, however, the wall is curved in regions of specimen thickness variation, reaching a maximum deviation from the basal plane of about 15 degrees in the thickest area observable. Attempts by magnetometry to observe a cone structure suggested by this behvaior have consistently led to the easy‐basal‐plane model for magnetization. However, while the anisotropy energy is large, it varies slowly with orientation within 20 deg of the basal plane. It is concluded that the substantial field arising from the free pole structure of the wedge‐shaped foil together with this peculiar anisotropy is responsible for large deviations of the domain magnetizations from the basal magnetizations from the basal plane, which the domain wall orientation reflects. It is important, therefore, in deducing magnetic details of such a material from TEM observations, to take due account of possible effects of the thin wedge geometry of the area observed.

The mechanical and magnetic properties of iron are closely related. In particular, cold working an annealed sample increases the mechanical hardness and decreases the magnetic permeability; conversely, recrystallization of the cold-worked sample will return these properties to their original levels. At any given level of applied fieldHa the larger the permeability, the larger is the magnetization and the external fieldHex of the specimen at any point external to the specimen. The curves of Fig. 1 show this effect for a variety of applied fields. It follows that any metallurgical process that changes the permeability can be continuously monitored by measuring the external field of the specimen. This study is directed at recovery and recrystallization.