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Ferromagnetism and domains
Intermediate
Aligned domains give strong magnetisation.
Ferromagnets contain microscopic domains with aligned atomic moments; an external field grows aligned domains and rotates others, giving a very large magnetisation.
Unmagnetised iron has random domains.
Strong exchange interaction needed.
In more detail
Ferromagnetic materials have regions called domains in which atomic moments align. In an unmagnetised sample, domains point in random directions, but a field can align them.
Real-world uses
- Transformer cores are made of ferromagnetic materials to guide flux.
- Hard drive platters store data in magnetic domains.
- Hard drives and speakers use ferromagnetic materials whose domains can be aligned and held in place.
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Frequently asked questions
What is a domain?
A region of uniform magnetisation inside a ferromagnetic material.
Can I see domains?
Yes, with special techniques such as Bitter patterns or electron microscopy.
What is a magnetic domain?
A small region in which the atomic magnetic moments are aligned in the same direction.
Related topics in Magnetism & Induction
Helmholtz coils · Magnetic dipole moment · Magnetic materials · Hysteresis · Curie temperature · Electromagnets