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Magnetic domain theory was developed by French physicist Pierre-Ernest Weiss [1] who, in 1906, suggested existence of magnetic domains in ferromagnets. [2] He suggested that large number of atomic magnetic moments (typically 10 12-10 18) [citation needed] were aligned parallel. The direction of alignment varies from domain to domain in a more ...
Paramagnetism, ferromagnetism, and spin waves. Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagnetic materials are noticeably attracted to a magnet ...
Micromagnetics simulations attempt to capture and explain in detail the space and time aspects of interacting magnetic domains, often based on the Landau-Lifshitz-Gilbert equation. Toy models such as the Ising model can help explain qualitative and thermodynamic aspects of hysteresis (such as the Curie point phase transition to paramagnetic ...
Even when Pierre Weiss did take the mantle of professor at Lyon, he later accepted the ETH Zurich proposal to become physics professor and director of the Institute of Physics in 1902. In 1907, he published an important work on the nature of ferromagnetism where he introduced the concept of molecular field, a precursor idea to mean field theory ...
Domain walls move easily within the magnet and have a low coercivity. By contrast, a particle that is single-domain in all magnetic fields changes its state by rotation of all the magnetization as a unit. This results in a much larger coercivity. The most widely used theory for hysteresis in single-domain particle is the Stoner–Wohlfarth model.
Ferrimagnetism has the same physical origins as ferromagnetism and antiferromagnetism. In ferrimagnetic materials the magnetization is also caused by a combination of dipole–dipole interactions and exchange interactions resulting from the Pauli exclusion principle .
These are examples of long-range magnetic ordering. They give rise to ferromagnetism, antiferromagnetism or ferrimagnetism, depending on the nature and relative orientations of the individual spins. [17] Compounds at temperatures below the Curie temperature exhibit long-range magnetic order in the form of ferromagnetism.
While mean field theory is a more reasonable model for ferromagnets at higher magnetic fields, the presence of more than one magnetic domain in real magnets means that especially at low magnetic fields, the experimentally measured macroscopic magnetic field (which is an average over the whole sample) will not be a reasonable way to determine ...