ferromagnetism

Examples of ferromagnetism in the following topics:

• Ferromagnetism

  • Ferromagnetism is the property of certain materials that enables them to form magnets and be attracted to magnets.
  • An everyday example of ferromagnetism is a refrigerator magnet used to hold notes on a refrigerator door.
  • Domains are small and randomly oriented in an unmagnetized ferromagnetic object.
  • Thus ferromagnetism only occurs in materials with partially filled shells.
  • Such materials are called ferromagnetic, after the Latin word for iron, ferrum.

• Ferromagnets and Electromagnets

  • Such magnets are called ferromagnets.
  • These materials are called ferromagnetic, after the Latin word ferrum (iron).
  • In an unmagnetized ferromagnetic object, domains are small and randomly oriented.
  • Due to the high magnetic permeability μ of the ferromagnetic material, the ferromagnetic core increases the magnetic field to thousands of times the strength of the field of the coil alone.
  • This is called a ferromagnetic-core or iron-core electromagnet.

• Permanent Magnets

  • Permanent magnets are objects made from ferromagnetic material that produce a persistent magnetic field.
  • Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic.
  • When a magnet is brought near a previously unmagnetized ferromagnetic material, it causes local magnetization of the material with unlike poles closest .
  • However, before magnetization these regions are small and randomly oriented throughout the unmagnetized ferromagnetic objects, so there is no net magnetic field.
  • This arrangement can become permanent when the ferromagnetic material is heated and then cooled.

• Solenoids, Current Loops, and Electromagnets

  • Combining a ferromagnet with an electromagnet can produce particularly strong magnetic effects.
  • Whenever strong magnetic effects are needed (such as lifting scrap metal, or in particle accelerators) electromagnets are enhanced by ferromagnetic materials.
  • Currents, including those associated with other submicroscopic particles like protons, allow us to explain ferromagnetism and all other magnetic effects.
  • Ferromagnetism, for example, results from an internal cooperative alignment of electron spins, possible in some materials but not in others.
  • An electromagnet induces regions of permanent magnetism on a floppy disk coated with a ferromagnetic material.

• Paramagnetism and Diamagnetism

  • Unlike ferromagnets, paramagnets do not retain any magnetization in the absence of an externally applied magnetic field, because thermal motion randomizes the spin orientations responsible for magnetism.
  • However, for materials that display some other form of magnetism (such as ferromagnetism or paramagnetism), the diamagnetic contribution becomes negligible.

• Transformers

  • A typical construction of a simple transformer has two coils wound on a ferromagnetic core that is laminated to minimize eddy currents.
  • Any change in current in the primary induces a current in the secondary.The figure shows a simple transformer with two coils wound on either sides of a laminated ferromagnetic core.

• Energy in a Magnetic Field

  • For hysteretic materials such as ferromagnets and superconductors, the work needed also depends on how the magnetic field is created.