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What is the hysteresis of a magnetic material?

Hysteresis is a concept that can affect a magnet. To do this you can consult the influence it has on the magnet in this article.

What is hysteresis?

This is a topic of ferromagnetic materials. The term comes from the Greek Hysteros, which means "behind". When an external magnet approaches, the magnetization of a ferromagnetic material increases rapidly. Because of this concept, the magnetization may not fall back so fast if the magnet is reduced. Removing the magnet completely leaves a remnant called remanence.

What influence does hysteresis have on the magnet?

Due to the delay, the magnetization of a ferromagnetic material is not fully proportional to the externally applied magnet. The delay can be influenced by the pretreatment of the material. For example, with a material, the delay is not double when the flux density is doubled. Above all, ferromagnetic materials remain magnetic after being magnetized. This residual magnetism is called remanance.

 ciclo de la histeresis

The magnetization of a ferromagnetic material initially increases with the application of an external magnet. At the same time, the magnetic power is also reduced when the magnetic field decreases. However, the reduction is slower than the scaling. Even a residual magnetization (remanence) is obtained if the external magnet is completely removed. It is a delay after the magnetic flux density and behind the magnetic field strength. There is a non-proportional relationship.

What should be considered in terms of hysteresis?

The hysteresis curve is a mathematical curve describing magnetic flux density B (magnetization). Depending on the applied external magnetic field H, the curve will be different for different materials and only applies to ferromagnetics.

The curve that describes the magnetic flux density of a material that has not yet been magnetized is called a new curve. In this case, both the magnetic flux density and the magnetization M of the material behave linearly with the induced magnet H and are calculated as follows:

M = (μ-1) - H.

In the formula, μ represents the magnetic permeability. The sum of magnetization of the material and indexed magnet H gives the internal magnetic field.

Another case is when the material is already magnetized. When the magnetic field is opposite to that of the body, the internal magnetic field will first be weakened. A remagnetization, i.e. a magnetization parallel to the indexed magnetic field occurs from the coercive field Hc, which does not increase linearly up to a limit, the saturation field strength BS. Due to the delay, the flux density decreases more slowly than it has increased when the external magnetic field weakens. And as described above, there remains a residual magnetism (BR).

 

The surface area of the hysteresis curve corresponds to the energy of magnetic flux density B and magnetic field H. It is the energy per unit volume that must be spent to pass the magnetization from the positive boundary (saturation flux density BS) and the negative boundary (saturation flux density BS) and the return path from the negative to the positive. This energy is exothermic, it is released in the form of heat. The harder the magnet, the greater the energy. Conversely, this means that hard materials are more resistant to small disturbances, such as other magnetic fields, shocks, heat, and so on. For this reason, hard materials are more suitable for permanent magnets. In the case of components where magnetization is used, for example in transformers, soft materials are used.

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