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The phenomenon of hysteresis in ferromagnetic materials is the result of two effects: rotation of magnetization and changes in size or number of magnetic domains.In general, the magnetization varies (in direction but not magnitude) across a magnet, but in sufficiently small magnets, it doesn't.
The curves form a hysteresis loop. Hysteresis is the dependence of the state of a system on its history. For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past. Plots of a single component of the moment often form a loop or hysteresis curve, where there are ...
In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Accordingly, physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume. [ 1 ]
Graphical definition of different coercivities in flux-vs-field hysteresis curve (B-H curve), for a hypothetical hard magnetic material. Equivalent definitions for coercivities in terms of the magnetization-vs-field (M-H) curve, for the same magnet.
Saturation is most clearly seen in the magnetization curve (also called BH curve or hysteresis curve) of a substance, as a bending to the right of the curve (see graph at right). As the H field increases, the B field approaches a maximum value asymptotically , the saturation level for the substance.
The relationship between magnetization and the magnetizing field is non-linear like in ferromagnetic materials. This fact is due to the contribution of the hysteresis loop, [4] which for ferromagnetic materials involves a residual magnetization.
As an electric field is applied the dipoles are forced to align and polarisation is created, when the electric field is removed polarisation remains. The hysteresis loop depends on temperature and as a result as the temperature is increased and reaches T 0 the two curves become one curve as shown in the dielectric polarisation (Figure 5). [52]
This magnetization as a function of an external field is described by a hysteresis curve. Although this state of aligned domains found in a piece of magnetized ferromagnetic material is not a minimal-energy configuration, it is metastable , and can persist for long periods, as shown by samples of magnetite from the sea floor which have ...