The area enclosed by the hysteresis loop is a measure of the energy required to reverse the magnetization in a material and is, therefore, a measure of magnetic coercivity. The coercivity can be affected by various factors such as temperature, stress, and impurities.
The coercivity of a material is affected by various factors such as temperature, stress, and impurities. The area enclosed by the hysteresis loop is a measure of the energy required to reverse the magnetization in a material and is, therefore, a measure of magnetic coercivity. Coercivity can be increased by introducing defects into the crystal lattice or applying an external magnetic field.
The hysteresis area is the difference in the magnetic flux density between the upper and lower operational limits of a ferromagnetic material. The hysteresis area predominantly determines the energy lost during repeated magnetization reversals and is usually specified as either kilojoule per cubic meter (kJ/m3) or joules per square meter of surface area (J/m2).
To calculate the area of hysteresis, first determine the magnetic flux density at both the upper and lower operational limits. The formula for magnetic flux density is:
B = μH
Where:
B is the magnetic flux density in webers per square meter (Wb/m2)
μ is the magnetic permeability in henries per meter (H/m)
H is the magnetic field strength in amperes per meter (A/m)
Once the magnetic flux density has been determined at both operational limits, the area of hysteresis can be calculated using the following formula:
A = B1 – B2
Where:
A is the area of hysteresis in joules per square meter (J/m2) or kilojoules per cubic meter (kJ/m3)
B1 is the upper operational limit of magnetic flux density in webers per square meter (Wb/m2)
B2 is the lower operational limit of magnetic flux density in webers per square meter (Wb/m2)
For example, if the upper operational limit of magnetic flux density is 1.2 teslas (T) and the lower operational limit is 0.8 T, the area of hysteresis would be:
A = B1 – B2
A = 1.2 T – 0.8 T
A = 0.4 T
The area of hysteresis measures the energy lost during repeated reversals of magnetization and is usually specified in either kilojoule per cubic meter (kJ/m3) or joules per square meter of surface area (J/m2). The formula for converting between these units is:
One kJ/m3 = 1,000,000 J/m2
So, in the example above, the hysteresis area would be 0.4 kJ/m3.
The hysteresis area is an important parameter in the design of magnetic materials and devices. A large area of hysteresis indicates that the material will lose a large amount of energy during repeated reversals of magnetization, leading to heating and reduced performance. Conversely, a small hysteresis area indicates that material will lose less energy during repeated magnetization reversals, making it more efficient. Therefore, it is important to select a magnetic material with the appropriate hysteresis area for the application.