This chapter contains sections titled: Introduction Molecular Field Theory Exchange Forces Band Theory Ferromagnetic Alloys Thermal Effects Theories of Ferromagnetism Magnetic Analysis 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
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
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.
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