The hysteresis loop is a graphical representation of the relationship between magnetic flux density (B) and magnetic field strength (H) in a magnetic material. It illustrates the behavior of the material when subjected to alternating magnetic fields. The shape and size of the hysteresis loop are influenced by several factors related to the magnetic circuit and electromagnetic properties of the material. Here are some factors that affect the shape and size of the hysteresis loop:
Material Properties: The fundamental property that affects the hysteresis loop is the type of magnetic material used. Ferromagnetic materials, such as iron and steel, exhibit larger hysteresis loops compared to paramagnetic or diamagnetic materials. This is because ferromagnetic materials have strong interactions between their atomic magnetic moments, resulting in significant hysteresis effects.
Saturation: Saturation refers to the point at which the magnetic material becomes fully magnetized, and further increase in magnetic field strength does not result in a significant increase in magnetic flux density. The saturation point influences the upper limits of the hysteresis loop and determines how much magnetic flux density the material can hold.
Coercivity (Hc): Coercivity is the measure of the magnetic field strength required to reduce the magnetic flux density to zero after the material has been saturated. Materials with higher coercivity will have wider hysteresis loops because they require more energy to demagnetize.
Remanence (Br): Remanence, also known as residual magnetization, is the magnetic flux density that remains in the material when the external magnetic field is removed after saturation. Higher remanence leads to a larger loop size in the vertical direction.
Frequency of Alternating Field: When the frequency of the alternating magnetic field increases, the hysteresis loop tends to narrow. This is because the material has less time to respond to the changing field, resulting in reduced energy losses.
Temperature: Temperature affects the magnetic properties of materials. As temperature increases, the hysteresis loop may expand or shift, affecting the shape and size of the loop.
Stress and Mechanical Strain: Mechanical stress and strain can alter the magnetic properties of a material and influence the hysteresis loop.
Grain Size and Microstructure: The microstructure of a material, including factors like grain size and crystallographic orientation, can affect the magnetic properties and the resulting hysteresis loop.
Impurities and Alloying Elements: The presence of impurities or alloying elements can modify the magnetic properties of a material and impact the hysteresis loop.
Applied Magnetic Field Strength: The magnitude of the external magnetic field applied to the material affects the overall size of the hysteresis loop. Increasing the field strength can lead to a larger loop.
In summary, the shape and size of the hysteresis loop are influenced by a combination of material properties, external factors, and operating conditions. Understanding these factors is crucial for designing and optimizing magnetic circuits and devices in various applications, such as transformers, inductors, and magnetic storage devices.