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Magnetic hysteresis occurs when an external magnetic field is applied to a ferromagnet such as iron and the atomic dipoles align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become magnetized. Once magnetized, the magnet will stay magnetized indefinitely.
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 ...
Assuming the external magnetic field is uniform and shares a common axis with the paramagnet, the extensive parameter characterizing the magnetic state is , the magnetic dipole moment of the system. The fundamental thermodynamic relation describing the system will then be of the form U = U ( S , V , I , N ) {\displaystyle U=U(S,V,I,N)} .
Typically the coercivity of a magnetic material is determined by measurement of the magnetic hysteresis loop, also called the magnetization curve, as illustrated in the figure above. The apparatus used to acquire the data is typically a vibrating-sample or alternating-gradient magnetometer. The applied field where the data line crosses zero is ...
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 maximum energy product is defined based on the magnetic hysteresis saturation loop (B-H curve), in the demagnetizing portion where the B and H fields are in opposition. It is defined as the maximal value of the product of B and H along this curve (actually, the maximum of the negative of the product, − BH , since they have opposing signs):
To lower its effects, an air gap is created in some kinds of transformer cores. [10] The saturation current, the current through the winding required to saturate the magnetic core, is given by manufacturers in the specifications for many inductors and transformers. On the other hand, saturation is exploited in some electronic devices.
In electromagnetism, the magnetic susceptibility (from Latin susceptibilis 'receptive'; denoted χ, chi) is a measure of how much a material will become magnetized in an applied magnetic field. It is the ratio of magnetization M ( magnetic moment per unit volume ) to the applied magnetic field intensity H .