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The Stoner–Wohlfarth model is a physical model explaining hysteresis in terms of anisotropic response ("easy" / "hard" axes of each crystalline grain). 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 .
In electromagnetism, the Preisach model of hysteresis is a model of magnetic hysteresis. Originally, it generalized hysteresis as the relationship between the magnetic field and magnetization of a magnetic material as the parallel connection of independent relay hysterons .
Usually only the hysteresis loop is plotted; the energy maxima are only of interest if the effect of thermal fluctuations is calculated. [1] The Stoner–Wohlfarth model is a classic example of magnetic hysteresis. The loop is symmetric (by a 180 ° rotation) about the origin and jumps occur at h = ± h s, where h s is known as the switching field.
Hysteresis can be a dynamic lag between an input and an output that disappears if the input is varied more slowly; this is known as rate-dependent hysteresis. However, phenomena such as the magnetic hysteresis loops are mainly rate-independent, which makes a durable memory possible.
Figure 1: The ideal magnetic hysteresis loop of an exchange spring magnet (dashed), as well as the hysteresis loops of its isolated hard (Blue) and soft (Red) components. H is the applied external magnetic field, M is the total magnetic flux density of the material.
Calculated magnetization curve for a superconducting slab, based on Bean's model. The superconducting slab is initially at H = 0. Increasing H to critical field H* causes the blue curve; dropping H back to 0 and reversing direction to increase it to -H* causes the green curve; dropping H back to 0 again and increase H to H* causes the orange curve.
Rowland's ring (aka Rowland ring) is an experimental arrangement for the measurement of the hysteresis curve of a sample of magnetic material. It was developed by Henry Augustus Rowland.
The stronger the external magnetic field H, the more the domains align, yielding a higher magnetic flux density B. Eventually, at a certain external magnetic field, the domain walls have moved as far as they can, and the domains are as aligned as the crystal structure allows them to be, so there is negligible change in the domain structure on ...