In addition to high permeability, its other magnetic properties are low coercivity, near zero magnetostriction, and significant anisotropicmagnetoresistance. 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. Permalloy's electrical resistivity can vary as much as 5% depending on the strength and the direction of an applied magnetic field. Permalloys typically have the face-centered cubic crystal structure with a lattice constant of approximately 0.355 nm in the vicinity of a nickel concentration of 80%. A disadvantage of permalloy is that it is not very ductile or workable, so applications requiring elaborate shapes, such as magnetic shields, are made of other high permeability alloys such as mu metal. Permalloy is used in transformerlaminations and magnetic recording heads.
Submarine telegraph cable wrapped with permalloy tape.
Permalloy was initially developed in the early 20th century for inductive compensation of telegraph cables.[3] When the first transatlantic submarine telegraph cables were laid in the 1860s, it was found that the long conductors caused distortion which reduced the maximum signalling speed to only 10–12 words per minute.[3] The right conditions for transmitting signals through cables without distortion were first worked out mathematically in 1885 by Oliver Heaviside.[4] It was proposed by Carl Emil Krarup in 1902 in Denmark that the cable could be compensated by wrapping it with iron wire, increasing the inductance and making it a loaded line to reduce distortion. However, iron did not have high enough permeability to compensate a transatlantic-length cable. After a prolonged search, permalloy was discovered in 1914 by Gustav Elmen of Bell Laboratories, who found it had higher permeability than silicon steel.[1] Later, in 1923, he found its permeability could be greatly enhanced by heat treatment.[5] A wrapping of permalloy tape could reportedly increase the signalling speed of a telegraph cable fourfold.[3]
This method of cable compensation declined in the 1930s, but by World War II many other uses for Permalloy were found in the electronics industry.
Other compositions
Other compositions of permalloy are available, designated by a numerical prefix denoting the percentage of nickel in the alloy, for example "45 permalloy" means an alloy containing 45% nickel, and 55% iron. "Molybdenum permalloy" is an alloy of 81% nickel, 17% iron and 2% molybdenum. The latter was invented at Bell Labs in 1940. At the time, when used in long distance copper telegraph lines, it allowed a tenfold increase in maximum line working speed.[4]Supermalloy, at 79% Ni, 16% Fe, and 5% Mo, is also well known for its high performance as a "soft" magnetic material, characterized by high permeability and low coercivity.
Supermalloy (a material with even higher magnetic permeability)
Notes
^ abElmen, G.W.; H. D. Arnold (July 1923). "Permalloy, A New Magnetic Material of Very High Permeability". Bell System Tech. J. USA: American Tel. & Tel. 2 (3): 101–111. doi:10.1002/j.1538-7305.1923.tb03595.x. Retrieved December 6, 2012.
^Jiles, David (1998). Introduction to Magnetism and Magnetic Materials. CRC Press. p. 354. ISBN978-0-412-79860-3.
^ abcGreen, Allen (2004). "150 Years Of Industry & Enterprise At Enderby's Wharf". History of the Atlantic Cable and Undersea Communications. FTL Design. Retrieved 2008-12-14.
^ abBragg, L. Electricity (London: G. Bell & Sons, 1943) pp. 212–213.
^Elmen, G.W. (January 1936). "Magnetic Alloys of Iron, Nickel, and Cobalt". Bell System Tech. J. USA: American Tel. & Tel. 15 (1): 113–135. doi:10.1002/j.1538-7305.1936.tb00721.x. Retrieved December 6, 2012.
References
Richard M. Bozorth, Ferromagnetism, Wiley-IEEE Press (1993 reissue), ISBN0-7803-1032-2.
P. Ciureanu and S. Middelhoek, eds., Thin Film Resistive Sensors, Institute of Physics Publishing (1992), ISBN0-7503-0173-2.
January 07, 2023
permalloy, nickel, iron, magnetic, alloy, with, about, nickel, iron, content, invented, 1914, physicist, gustav, elmen, bell, telephone, laboratories, notable, very, high, magnetic, permeability, which, makes, useful, magnetic, core, material, electrical, elec. 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 Commercial permalloy alloys typically have relative permeability of around 100 000 compared to several thousand for ordinary steel 2 Strip of permalloy In addition to high permeability its other magnetic properties are low coercivity near zero magnetostriction and significant anisotropic magnetoresistance 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 Permalloy s electrical resistivity can vary as much as 5 depending on the strength and the direction of an applied magnetic field Permalloys typically have the face centered cubic crystal structure with a lattice constant of approximately 0 355 nm in the vicinity of a nickel concentration of 80 A disadvantage of permalloy is that it is not very ductile or workable so applications requiring elaborate shapes such as magnetic shields are made of other high permeability alloys such as mu metal Permalloy is used in transformer laminations and magnetic recording heads Contents 1 Development 2 Other compositions 3 See also 4 Notes 5 ReferencesDevelopment Edit Submarine telegraph cable wrapped with permalloy tape Permalloy was initially developed in the early 20th century for inductive compensation of telegraph cables 3 When the first transatlantic submarine telegraph cables were laid in the 1860s it was found that the long conductors caused distortion which reduced the maximum signalling speed to only 10 12 words per minute 3 The right conditions for transmitting signals through cables without distortion were first worked out mathematically in 1885 by Oliver Heaviside 4 It was proposed by Carl Emil Krarup in 1902 in Denmark that the cable could be compensated by wrapping it with iron wire increasing the inductance and making it a loaded line to reduce distortion However iron did not have high enough permeability to compensate a transatlantic length cable After a prolonged search permalloy was discovered in 1914 by Gustav Elmen of Bell Laboratories who found it had higher permeability than silicon steel 1 Later in 1923 he found its permeability could be greatly enhanced by heat treatment 5 A wrapping of permalloy tape could reportedly increase the signalling speed of a telegraph cable fourfold 3 This method of cable compensation declined in the 1930s but by World War II many other uses for Permalloy were found in the electronics industry Other compositions EditOther compositions of permalloy are available designated by a numerical prefix denoting the percentage of nickel in the alloy for example 45 permalloy means an alloy containing 45 nickel and 55 iron Molybdenum permalloy is an alloy of 81 nickel 17 iron and 2 molybdenum The latter was invented at Bell Labs in 1940 At the time when used in long distance copper telegraph lines it allowed a tenfold increase in maximum line working speed 4 Supermalloy at 79 Ni 16 Fe and 5 Mo is also well known for its high performance as a soft magnetic material characterized by high permeability and low coercivity See also EditLoading coil Mu metal Sendust Supermalloy a material with even higher magnetic permeability Notes Edit a b Elmen G W H D Arnold July 1923 Permalloy A New Magnetic Material of Very High Permeability Bell System Tech J USA American Tel amp Tel 2 3 101 111 doi 10 1002 j 1538 7305 1923 tb03595 x Retrieved December 6 2012 Jiles David 1998 Introduction to Magnetism and Magnetic Materials CRC Press p 354 ISBN 978 0 412 79860 3 a b c Green Allen 2004 150 Years Of Industry amp Enterprise At Enderby s Wharf History of the Atlantic Cable and Undersea Communications FTL Design Retrieved 2008 12 14 a b Bragg L Electricity London G Bell amp Sons 1943 pp 212 213 Elmen G W January 1936 Magnetic Alloys of Iron Nickel and Cobalt Bell System Tech J USA American Tel amp Tel 15 1 113 135 doi 10 1002 j 1538 7305 1936 tb00721 x Retrieved December 6 2012 References EditRichard M Bozorth Ferromagnetism Wiley IEEE Press 1993 reissue ISBN 0 7803 1032 2 P Ciureanu and S Middelhoek eds Thin Film Resistive Sensors Institute of Physics Publishing 1992 ISBN 0 7503 0173 2 Retrieved from https en wikipedia org w index php title Permalloy amp oldid 1111646416, wikipedia, wiki, book, books, library,
