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A useful tool for dealing with high frequency magnetic effects is the complex permeability. While at low frequencies in a linear material the magnetic field and the auxiliary magnetic field are simply proportional to each other through some scalar permeability, at high frequencies these quantities will react to each other with some lag time. [36]
Each layer is about 5 mm thick. It reduces the effect of the Earth's magnetic field inside by a factor of 1500. Mu-metal is a nickel–iron soft ferromagnetic alloy with very high permeability, which is used for shielding sensitive electronic equipment against static or low-frequency magnetic fields.
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.
It is a high permeability ferromagnetic alloy used in magnetic cores and magnetic shielding in electrical components, such as pulse transformers and ultra-sensitive magnetic amplifiers. It has a resistivity of 0.6 Ω·mm 2 /m (or 6.0 x 10 −7 Ω·m), [1] an extremely high relative magnetic permeability (approximately 800 000), and a low ...
[1] [2] [15] [16] A core can increase the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability of the material. [ 1 ] [ 2 ] Not all electromagnets use cores, so this is called a ferromagnetic-core or iron-core electromagnet.
In other words, the easy axis is an energetically favorable direction of spontaneous magnetization. Because the two opposite directions along an easy axis are usually equivalently easy to magnetize along, the actual direction of magnetization can just as easily settle into either direction, which is an example of spontaneous symmetry breaking.
They also have high magnetic permeability. These so-called ceramic magnets are cheap, and are widely used in household products such as refrigerator magnets . The maximum magnetic field B is about 0.35 tesla and the magnetic field strength H is about 30–160 kiloampere turns per meter (400–2000 oersteds ). [ 33 ]
For example, high permeability iron alloys used in transformers reach magnetic saturation at 1.6–2.2 teslas (T), [4] whereas ferrites saturate at 0.2–0.5 T. [5] Some amorphous alloys saturate at 1.2–1.3 T. [6] Mu-metal saturates at around 0.8 T. [7] [8] Due to saturation, the magnetic permeability μ f of a ferromagnetic substance reaches ...