The area of the hysteresis loop represents the amount of energy lost per cycle of magnetization in a magnetic material. This energy loss occurs due to molecular friction as the magnetic domains within the material are repeatedly realigned during magnetization and demagnetization cycles. The energy lost is dissipated as heat, known as hysteresis loss. More specifically, the energy loss per unit volume per cycle is given by the integral ∫H dB\int H,dB∫HdB, which corresponds to the area enclosed by the B-H (magnetic flux density vs. magnetizing force) hysteresis loop. Thus, a larger hysteresis loop area indicates greater energy loss in the material during each magnetization cycle. For example, steel typically has a larger hysteresis loop area and thus higher energy loss compared to soft iron, which has a narrower loop and lower loss. This characteristic is important in applications: materials with small hysteresis loop areas (soft magnetic materials) are preferred in transformers and electric motors to minimize energy dissipation, while materials with large loop areas (hard magnetic materials) are useful for permanent magnets and memory storage devices due to their high retentivity and coercivity. In summary:

• The area of the hysteresis loop measures the energy lost per cycle of magnetization.
• This energy loss is due to internal friction in the material as magnetic domains realign.
• The loss manifests as heat and is proportional to the loop area.
• Soft magnetic materials have small loop areas and low losses; hard magnetic materials have large loop areas and high losses