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Views Read Edit View history. It is a “soft” ferromagnetic material; it has low magnetic anisotropy and magnetostriction giving it a low coercivity so that it saturates at low magnetic fields. It has several compositions. Introduction to Magnetism and Magnetic Materials. From Wikipedia, the free encyclopedia. Other materials with similar magnetic properties include Co-Netic, supermalloysupermumetal, nilomag, magnetlc, molybdenum permalloySendustM, Hipernom, HyMu and Amumetal.
Mu-metal – Wikipedia
Bending or mechanical shock after annealing may disrupt the material’s grain alignment, leading to a drop in the permeability of the affected areas, which can be restored by repeating the hydrogen annealing step.
Telcon invented mu-metal to compete with permalloythe first high-permeability alloy used for cable compensation, whose patent rights were held by competitor Western Electric.
Thus, the best shape for shields daviv a closed container surrounding the shielded space. At the time, when used in long distance copper telegraph lines, it allowed a tenfold increase in maximum line working speed. Mu-metal typically has relative permeability values of 80,—, compared to several thousand for ordinary steel.
From Wikipedia, the free rownload.
Permalloy – Wikipedia
This page was last edited on 7 Februaryat Invented in by physicist Gustav Elmen at Bell Telephone Laboratories matnetism is notable for its very high magnetic permeabilitywhich makes it useful as a magnetic core material in electrical and electronic equipment, and also in magnetic shielding to block magnetic fields. After a prolonged search, permalloy was discovered in by Gustav Pvf of Bell Laboratorieswho found it had higher permeability than silicon steel.
All articles with dead external links Articles with dead external links from February Articles with permanently dead external links All articles with unsourced statements Articles with unsourced statements from February Nickel alloys Magnetic alloys Ferromagnetic materials Named alloys. Mu-metal was developed by British scientists Willoughby Jile. However, iron did not have high enough permeability to compensate a transatlantic-length cable.
The low magnetostriction is critical for industrial applications, allowing it to be used in thin films where variable stresses would otherwise cause a ruinously large variation in magnetic properties.
This gives it low hysteresis losses when used in AC magnetic circuits. Mu-metal objects require heat treatment after they are in final form— annealing in a magnetic field in hydrogen atmosphere, which increases the magnetic permeability about 40 times. Magnetic shielding made with high-permeability alloys like mu-metal works not by blocking magnetic fields but by providing a path for the magnetic field lines around the shielded area.
Permalloys typically have the face centered cubic crystal structure with a lattice constant of approximately 0. Its higher saturation value allows it to handle stronger magnetic fields, reducing them to a lower level that can be shielded effectively by the inner mu-metal layers.
History of the Introduction to magnetism and magnetic materials david jiles pdf download Cable and Undersea Communications. Mu-metal was developed by adding copper to permalloy to improve ductility.
Retrieved from ” https: History of the Atlantic Cable and Undersea Communications. Retrieved December 6, Smith and Henry J.
Garnett    and patented in for inductive loading of submarine telegraph cables by The Telegraph Construction and Maintenance Co. The bandwidth could be increased by adding inductance to compensate.
The latter was invented at Bell Labs in The high permeability of mu-metal provides a low reluctance path for magnetic fluxleading to its use in magnetic shields against static or slowly varying magnetic fields. RF magnetic fields above about kHz can be shielded by Mangetism shields: Retrieved from ” https: This was first done by wrapping the introduction to magnetism and magnetic materials david jiles pdf download with a helical wrapping of metal tape or wire of high magnetic permeability, which confined the magnetic field.
Views Read Edit View history. This method of cable compensation declined in the s, but by World War 2 many other uses for Permalloy were found in the electronics industry. Thus, mu-metal shields are often made of several enclosures one inside the other, each of which successively reduces the field inside it. This page was last edited on 25 Juneat In the s this use for mu-metal declined, but by World War II many other uses were found in the electronics industry particularly maetrials for transformers and cathode ray tubesas well as the fuzes inside magnetic mines.
Handbook of Chemistry and Physics 64th ed. Not to be confused with nu metal. In addition to high permeability, its other materiqls properties are low coercivitynear zero magnetostrictionand significant anisotropic magnetoresistance.