[[Electrodynamics MOC]]
# Ferromagnetism
**Ferromagnetism** is a special kind of magnetism exhibited by some materials,
including the familiar examples of iron and nickel cobalt.
Due to strong interactions between the [[Magnetic dipole moment|magnetic moments]] of atoms,
large regions within the substance line up their moments into what's known as a **magnetic domain**.
When an external magnetic field is applied, 
each domain experiences a torque that forces them to align with the external field,
and hence the material is drawn towards the magnet.

Ferromagnetic substances can be classified by 
whether they retain this alignment once this external $\vab B$-field is gone
- **Hard ferromagnetic materials** retain alignment
- **Soft magnetic fields** return to a disordered state

The ferromagnetic properties of a substance depend on temperature,
as higher temperatures increase disorder in the substance 
preventing domain formation.
The temperature at which a substance is no longer magnetic is called its **Curie temperature**.

Like [[Paramagnetism]], ferromagnetism arises from unpaired electrons in the outer shell of an atom.

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#state/tidy | #SemBr