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Engineering LibreTexts

Magnetic Properties

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  • Magnetism is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the fundamental magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. All materials are influenced to some extent by a magnetic field.

    • Antiferromagnetism
      Antiferromagnetic are like ferromagnets but their magnetic moments align antiparallel to the neighboring moments. This alignment occurs spontaneously below a critical temperature known as the Neel temperature. Above the Neel temperature the material becomes paramagnetic. Antiferromagnets are less common compared to the other types of magnetic behaviors, and are mostly observed at low temperatures.
    • Diamagnetism
      Diamagnetic behavior is the change in orbital angular momentum induced by an external magnetic field. All materials exhibit a diamagnetic response, and it may be understood as the attempt to expel the applied magnetic field. The physical manifestation of these effects can be appreciated when a diamagnetic material is placed in the presence of a magnetic field and a force repels the material
    • Ferrimagnetism
      Magnetic properties of materials are often utilized in advance technological devices such as superconductive Maglev trains, scanning electron microscopy, electron beam physical vapor deposition, and internal and external computer hard drives. There are five types of magnetism: diamagnetism, paramagnetism, ferromagnetism, antiferromagnetism, and ferrimagnetism.
    • Ferromagnetism
      In ferromagnetism the spins of the electrons are all pointing in the same direction. This is what causes permanent magnets to attract through opposite poles, south to north and vise versa, as well as repel when the same poles are facing each other.
    • Magnetic Domains
      The magnetic moments of atoms dictate the magnetic properties of a material. In ferromagnetic materials, long range alignments of magnetic moments, called domains, contain magnetic moments that all point in the same direction. However, if a material were to have all of its magnetic moments pointed in the same direction, this would create a very large external magnetic field. This field is not energetically minimizing as it stores large amounts of magnetostatic energy in the field.
    • Magnetic Hysteresis
      A magnetic hysteresis, otherwise known as a hysteresis loop, is a representation of the magnetizing force (H) versus the magnetic flux density (B) of a ferromagnetic material. The curvature of the hysteresis is characteristic of the type of material being observed and can vary in size and shape.
    • Magnetic Memory
    • Magnetostriction
      Magnetostriction is a property of ferromagnetic materials which causes them to expand or contract in response to a magnetic field. This effect allows magnetostrictive materials to convert electromagnetic energy into mechanical energy. As a magnetic field is applied to the material, its molecular dipoles and magnetic field boundaries rotate to align with the field. This causes the material to strain and elongate.
    • Meissner Effect
      One phenomena that occurs in superconductors below the critical temperature is the Meissner effect, which is where a superconductor expels all magnetic field from within itself. One of the most well known demonstrations of the Meissner effect is its ability to make a magnet levitate above a superconductor.
    • Superparamagnetism
      Superparamagnetism is a form of magnetism exhibited by small ferromagnetic or ferrimagnetic nanoparticles. At sizes of less than a hundred nanometers, the nanoparticles are single-domain particles, allowing the magnetization of the nanoparticles to be approximated as one giant magnetic moment by summing the individual magnetic moments of each constituent atom.