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Coercivity in a ferromagnetic material is the intensity of the applied magnetic field (H field) required to demagnetize that material, after the magnetization of the sample has been driven to saturation by a strong field. This demagnetizing field is applied opposite to the original saturating field.
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, which is a consequence of their substantial ...
When the coercivity of the material parallel to an applied field is the smaller of the two, the differential susceptibility is a function of the applied field and self interactions, such as the magnetic anisotropy. When the material is not saturated, the effect will be nonlinear and dependent upon the domain wall configuration of the material.
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.
Magnetocrystalline anisotropy has a great influence on industrial uses of ferromagnetic materials. Materials with high magnetic anisotropy usually have high coercivity, that is, they are hard to demagnetize. These are called "hard" ferromagnetic materials and are used to make permanent magnets.
Hysteresis loop Induction B as function of field strength H for H varying between H min and H max; for ferromagnetic material the B has different values for H going up and down, therefore a plot of the function forms a loop instead of a curve joining two points; for perminvar type materials, the loop is a "rectangle" (Domain Structure of Perminvar Having a Rectangular Hysteresis Loop, Williams ...
The net effect (in most materials) is that the electrical resistance has maximum value when the direction of current is parallel to the applied magnetic field. [9] AMR of new materials is being investigated and magnitudes up to 50% have been observed in some uranium (but otherwise quite conventional) ferromagnetic compounds. [10]
Neodymium has a negative coefficient, meaning the coercivity along with the magnetic energy density (BH max) decreases as temperature increases. Neodymium-iron-boron magnets have high coercivity at room temperature, but as the temperature rises above 100 °C (212 °F), the coercivity decreases drastically until the Curie temperature (around 320 ...