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A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic).
A ferrimagnetic material is a material that has populations of atoms with opposing magnetic moments, as in antiferromagnetism, but these moments are unequal in magnitude, so a spontaneous magnetization remains. [1] This can for example occur when the populations consist of different atoms or ions (such as Fe 2+ and Fe 3+).
Paramagnetic materials have a weak induced magnetization in a magnetic field, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization in a magnetic field, and can be magnetized to have magnetization in the absence of an external field, becoming a permanent magnet. Magnetization is ...
A plastic magnet is a non-metallic magnet made from an organic polymer.. Plastic magnets could be used in computer hardware such as disc drives, as well as in medical devices such as pacemakers and cochlear implants, where the organic material is more likely to be biocompatible than its metallic counterparts.
[example needed] [clarification needed] The magnetic material known as "Zn Fe" has the formula Zn Fe 2 O 4, with Fe 3+ occupying the octahedral sites and Zn 2+ occupying the tetrahedral sites, it is an example of normal structure spinel ferrite. [18] [page needed] Some ferrites adopt hexagonal crystal structure, like barium and strontium ...
The magnetic alloy material is formed by splat quenching onto a water-cooled drum. This metal ribbon is crushed to a powder and then heat-treated to improve its coercivity . The powder is mixed with a polymer to form a mouldable putty, similar to a glass-filled polymer .
The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ. The effect was first identified in 1842 by James Joule when observing a sample of iron. [1] Magnetostriction applies to magnetic fields, while electrostriction applies to electric fields.
To place multiferroic materials in their appropriate historical context, one also needs to consider magnetoelectric materials, in which an electric field modifies the magnetic properties and vice versa. While magnetoelectric materials are not necessarily multiferroic, all ferromagnetic ferroelectric multiferroics are linear magnetoelectrics ...