Hysteresis in magnetism describes the phenomenon where a material’s magnetization lags behind changes in the applied magnetic field. When a magnetic field is applied to a ferromagnetic material, its magnetic domains begin to align, increasing the overall magnetization. However, when the external field is reduced or reversed, the domains do not immediately return to their original state. Instead, the material retains some magnetization, known as remanence.
To fully demagnetize the material, a coercive field (a field in the opposite direction) must be applied. Plotting the magnetization against the applied magnetic field produces a hysteresis loop, which shows this lagging behavior and the energy lost in the form of heat during each cycle of magnetization and demagnetization.
Key characteristics of magnetic hysteresis:
- Remanent magnetization: The residual magnetism after the field is removed.
- Coercivity: The required reverse field to bring magnetization to zero.
- Energy loss: Represented by the area inside the hysteresis loop.
Hysteresis is crucial in:
- Permanent magnets (which require high remanence and coercivity),
- Magnetic memory devices (like hard drives),
- Transformers and motors, where minimizing hysteresis loss improves efficiency.
This “memory effect” reflects the material’s magnetic history and plays a vital role in both magnetic material design and electromagnetic system performance.