Ferromagnetic materials are strong magnets. These materials have the ability to retain a strong magnetic field even after the external magnetic field is removed. This property makes them ideal for various applications such as electromagnets, transformers, and magnetic storage devices.

Here is a detailed explanation of why ferromagnetic materials are strong magnets:

1. Definition of Ferromagnetism:
- Ferromagnetism is a property exhibited by certain materials that have a spontaneous magnetic moment even in the absence of an external magnetic field.
- In other words, these materials have a high susceptibility to magnetization.

2. Magnetic Domains:
- Ferromagnetic materials are made up of tiny regions called magnetic domains.
- Each domain acts as a tiny magnet with its own magnetic moment.
- In an unmagnetized state, the magnetic moments of these domains are randomly oriented, causing the overall magnetization to be zero.

3. Alignment of Magnetic Domains:
- When a ferromagnetic material is placed in an external magnetic field, the magnetic domains start aligning themselves with the applied field.
- This alignment is due to the interaction between the magnetic moments of the domains and the external magnetic field.
- As the alignment progresses, the material becomes magnetized, and the magnetic moments of the domains reinforce each other.

4. Spontaneous Magnetization:
- Even after removing the external magnetic field, the aligned magnetic domains remain in their positions due to strong interatomic forces.
- This phenomenon is known as spontaneous magnetization.
- As a result, the ferromagnetic material retains a significant magnetic field and behaves as a strong magnet.

5. Hysteresis Loop:
- The behavior of ferromagnetic materials can be represented by a hysteresis loop, which shows the relationship between the magnetic field strength and the magnetization.
- The loop demonstrates the phenomenon of hysteresis, where the magnetization lags behind the magnetic field strength during the magnetization and demagnetization processes.
- The area enclosed by the hysteresis loop represents the energy loss during the magnetization cycles.

In conclusion, ferromagnetic materials exhibit strong magnetism due to the alignment and retention of magnetic domains even after the external magnetic field is removed. This property makes them valuable for a wide range of applications requiring permanent magnets and magnetic storage.