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3, is in between soft and hard magnetic material and is usually classified as a semi-hard material. [23] It is mainly used for its magnetostrictive applications like sensors and actuators [24] thanks to its high saturation magnetostriction (~200 ppm). Co Fe 2 O 4 has also the benefits to be rare-earth free, which makes it a good substitute for ...
For materials satisfying M = χH, we can also write B = μ 0 (1 + χ)H = μ 0 μ r H = μH, where μ r = 1 + χ is the (dimensionless) relative permeability and μ =μ 0 μ r is the magnetic permeability. Both hard and soft magnets have a more complex, history-dependent, behavior described by what are called hysteresis loops, which give either ...
To demagnetize a saturated magnet, a magnetic field must be applied. The threshold at which demagnetization occurs depends on the coercivity of the material. Magnetically hard materials have high coercivity, whereas magnetically soft materials have low coercivity.
"Soft" magnetic materials with low coercivity and hysteresis, such as silicon steel, or ferrite, are usually used in cores. Magnetic field (green) created by a current-carrying winding (red) in a typical magnetic core transformer or inductor, with the iron core C forming a closed loop, possibly with air gaps G in it. The drawing shows a section ...
The coercivity is a measure of the degree of magnetic hysteresis and therefore characterizes the lossiness of soft magnetic materials for their common applications. The saturation remanence and coercivity are figures of merit for hard magnets, although maximum energy product is also commonly quoted.
Strip of permalloy. Permalloy is a nickel–iron magnetic alloy, with about 80% nickel and 20% iron content.Invented in 1914 by physicist Gustav Elmen at Bell Telephone Laboratories, [1] it is notable for its very high magnetic permeability, which makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields.
Mu-metal is used to shield equipment from magnetic fields. For example: Electric power transformers, which are built with mu-metal shells to prevent them from affecting nearby circuitry. Hard disks, which have mu-metal backings to the magnets found in the drive to keep the magnetic field away from the disk. [6]
An electropermanent magnet or EPM is a type of permanent magnet in which the external magnetic field can be switched on or off by a pulse of electric current in a wire winding around part of the magnet. The magnet consists of two sections, one of "hard" (high coercivity) magnetic material and one of "soft" (low coercivity) material. The ...