Ferromagnetism is a powerful form of magnetism that occurs when the magnetic moments of atoms in a material align in the same direction, even without an external magnetic field. This alignment creates magnetic domains—regions where the atomic magnetic moments are uniformly oriented.
In ferromagnetic materials like iron, cobalt, and nickel, the interactions between neighboring atomic spins (called exchange interactions) favor this parallel alignment. When many domains align under an external magnetic field, the material becomes strongly magnetized. Even after the field is removed, the domains often remain aligned, resulting in permanent magnetism.
Key features of ferromagnetism:
- Very high magnetic susceptibility.
- Spontaneous magnetization below a critical temperature known as the Curie temperature.
- Ability to become and stay magnetized (used in permanent magnets).
Ferromagnetism is essential in:
- Electric motors, transformers, and generators,
- Data storage devices like hard drives,
- Magnetic sensors and memory technologies.
This phenomenon lies at the heart of many modern technologies, making it one of the most practically significant types of magnetism.