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Soft materials are important in a wide range of technological applications, and each soft material can often be associated with multiple disciplines. Liquid crystals, for example, were originally discovered in the biological sciences when the botanist and chemist Friedrich Reinitzer was investigating cholesterols. [10]
Most non-magnetic materials have a relatively small χ (on the order of a millionth), but soft magnets can have χ on the order of hundreds or thousands. For materials satisfying M = χ H , we can also write B = μ 0 (1 + χ ) H = μ 0 μ r H = μ H , where μ r = 1 + χ is the (dimensionless) relative permeability and μ =μ 0 μ r is the ...
Ferromagnetic materials with high coercivity are called magnetically hard, and are used to make permanent magnets. Materials with low coercivity are said to be magnetically soft. The latter are used in transformer and inductor cores, recording heads, microwave devices, and magnetic shielding.
"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 ...
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]
The response of the magnetic moment to a magnetic field boosts the response of the coil wrapped around it. Low coercivity reduces that energy loss associated with hysteresis. Magnetic hysteresis material (soft nickel-iron rods) has been used in damping the angular motion of satellites in low Earth orbit since the dawn of the space age. [5]
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.
Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization.The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ.