38:
267:, at high field strengths. Thus, mu-metal shields are often made of several enclosures one inside the other, each of which successively reduces the field inside it. Because mu-metal saturates at relatively low fields, sometimes the outer layer in such multilayer shields is made of ordinary steel. 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.
46:
446:
229:
489:. 80 kilometres (50 mi) of fine mu-metal wire were needed for each 1.6 km of cable, creating a great demand for the alloy. The first year of production Telcon was making 30 tons per week. In the 1930s this use for mu-metal declined, but by World War II many other uses were found in the
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The alloy has a low coercivity, near zero magnetostriction, and significant anisotropic magnetoresistance. The low magnetostriction is critical for industrial applications, where variable stresses in thin films would otherwise cause a ruinously large variation in magnetic properties.
712:
219:
boundaries. 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.
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by The
Telegraph Construction and Maintenance Co. Ltd. (now Telcon Metals Ltd.), a British firm that built the Atlantic undersea telegraph cables. The conductive seawater surrounding an undersea cable added a significant
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are used for similar purposes, and have even higher permeability at high frequencies, but are brittle and nearly non-conductive, so can only replace mu-metals where conductivity and pliability aren't required.
256:
against static or slowly varying magnetic fields. Magnetic shielding made with high-permeability alloys like mu-metal works not by blocking magnetic fields but by providing a path for the
474:
to compensate. This was first done by wrapping the conductors with a helical wrapping of metal tape or wire of high magnetic permeability, which confined the magnetic field.
141:) which represents permeability in physics and engineering formulas. A number of different proprietary formulations of the alloy are sold under trade names such as
509:. Telcon Metals Ltd. abandoned the trademark "MUMETAL" in 1985. The last listed owner of the mark "MUMETAL" is Magnetic Shield Corporation, Illinois.
843:
710:, "New and improved magnetic alloys and their application in the manufacture of telegraphic and telephonic cables", issued 1927-10-27
263:
The effectiveness of mu-metal shielding decreases with the alloy's permeability, which drops off at both low field strengths and, due to
49:
Five-layer mu-metal box. Each layer is about 5 mm thick. It reduces the effect of the Earth's magnetic field inside by a factor of 1500.
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Mu-metal is a soft magnetic alloy with exceptionally high magnetic permeability. The high permeability of mu-metal provides a low
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values of 80,000–100,000 compared to several thousand for ordinary steel. It is a "soft" ferromagnetic material; it has low
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around the shielded area. Thus, the best shape for shields is a closed container surrounding the shielded space.
157:
453:
Mu-metal was developed by
British scientists Willoughby S. Smith and Henry J. Garnett and patented in 1923 for
325:, which have mu-metal backings to the magnets found in the drive to keep the magnetic field away from the disk.
532:
481:, the first high-permeability alloy used for cable compensation, whose patent rights were held by competitor
467:
184:, malleable and workable, allowing it to be easily formed into the thin sheets needed for magnetic shields.
662:
Daniels, Ryan J.; McIntyre, Timothy; Kisner, Roger; Killough, Stephen; Lenarduzzi, Roberto (April 2015).
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458:
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116:
More recently, mu-metal is considered to be ASTM A753 Alloy 4 and is composed of approximately
872:
17:
664:"Design and implementation of a Hall Effect sensor array applied to recycling hard drive magnets"
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and slowed signaling speed to 10–12 words per minute. The bandwidth could be increased by adding
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335:, which have mu-metal shields to prevent stray magnetic fields from deflecting the electron beam.
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when used in AC magnetic circuits. Other high-permeability nickel–iron alloys such as
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is used similarly in some transformers as a cheaper, less permeable option.
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have similar magnetic properties; mu-metal's advantage is that it is more
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Mu-metal has several compositions. One such composition is approximately
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Mu-metal is used to shield equipment from magnetic fields. For example:
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Other materials with similar magnetic properties include Co-Netic,
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485:. Mu-metal was developed by adding copper to permalloy to improve
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to the cable, causing distortion of the signal, which limited the
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so that it saturates at low magnetic fields. This gives it low
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68:
760:"150 Years Of Industry & Enterprise At Enderby's Wharf"
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61:
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764:
History of the
Atlantic Cable and Undersea Communications
341:, which have a mu-metal case to reduce interference when
41:
Assortment of mu-metal shapes used in electronics, 1951
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about 40 times. The annealing alters the material's
748:, filed January 10, 1924, granted September 8, 1925
859:
744:Willoughby Statham Smith, Henry Joseph Garnett,
732:, filed January 10, 1924, granted April 27, 1926
728:Willoughby Statham Smith, Henry Joseph Garnett,
534:Introduction to Magnetism and Magnetic Materials
289:materials can also expel magnetic fields by the
126:small amounts of various other elements such as
417:, supermumetal, nilomag, sanbold, molybdenum
735:
719:
809:"Trademark Status & Document Retrieval"
785:"Trademark Status & Document Retrieval"
700:
562:(64th ed.). CRC Press. p. E-108.
425:, M-1040, Hipernom, HyMu-80 and Amumetal.
382:, for example, photoelectron spectroscopy.
477:Telcon invented mu-metal to compete with
211:and removing some impurities, especially
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227:
215:, which obstruct the free motion of the
137:The name came from the Greek letter mu (
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640:. Magnetic Shield Corp. Archived from
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449:Mu-metal submarine cable construction
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408:
396:Fluxgate magnetometers and compasses
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240:, from a 1945 electronics magazine
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853:Info about using mu metal shields
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560:Handbook of Chemistry and Physics
378:for experiments with low-energy
273:magnetic fields above about 100
199:atmosphere, which increases the
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751:
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339:Magnetic phonograph cartridges
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133:12~15% iron for the remainder.
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1:
634:"Magnetic Fields and Shields"
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191:after they are in final form—
82:
493:(particularly shielding for
7:
304:
10:
894:
676:10.1109/SECON.2015.7132879
537:. CRC Press. p. 354.
459:submarine telegraph cables
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349:Magnetic resonance imaging
29:
609:"Mu Metal specifications"
187:Mu-metal objects require
615:. Nick Murby. 2009-03-25
613:Shielding Specifications
388:circuits and especially
252:, leading to its use in
30:Not to be confused with
878:Ferromagnetic materials
195:in a magnetic field in
156:Mu-metal typically has
558:Weast, Robert (1983).
450:
398:as part of the sensor.
360:magnetoencephalography
241:
50:
42:
758:Green, Allen (2004).
531:Jiles, David (1998).
448:
370:Photomultiplier tubes
232:Mu-metal shields for
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201:magnetic permeability
158:relative permeability
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40:
491:electronics industry
258:magnetic field lines
841:Zero gauss chambers
836:Mu-Metal Properties
364:magnetocardiography
277:can be shielded by
162:magnetic anisotropy
846:2013-02-17 at the
501:), as well as the
451:
390:Josephson junction
242:
168:, giving it a low
51:
43:
742:US Patent 1552769
726:US Patent 1582353
685:978-1-4673-7300-5
668:SoutheastCon 2015
569:978-0-8493-0463-7
544:978-0-412-79860-3
499:cathode-ray tubes
409:Similar materials
402:Proximity sensors
331:used in analogue
329:Cathode-ray tubes
234:cathode-ray tubes
205:crystal structure
174:hysteresis losses
16:(Redirected from
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483:Western Electric
427:Electrical steel
404:(inductive type)
351:(MRI) equipment.
345:are played back.
254:magnetic shields
166:magnetostriction
27:Trademark, alloy
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386:Superconducting
376:Vacuum chambers
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291:Meissner effect
287:Superconducting
283:electric fields
279:Faraday shields
236:(CRTs) used in
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217:magnetic domain
207:, aligning the
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77:magnetic fields
71:with very high
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746:Magnetic Alloy
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590:. Josh Wickler
584:"MuMetal Home"
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297:temperatures.
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123:5% molybdenum,
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816:. Retrieved
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768:. Retrieved
766:. FTL Design
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646:. Retrieved
642:the original
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617:. Retrieved
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592:. Retrieved
588:mu-metal.com
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495:transformers
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317:transformers
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73:permeability
53:
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464:capacitance
457:loading of
415:supermalloy
224:Application
120:80% nickel,
91:77% nickel,
862:Categories
818:2017-07-28
794:2017-07-28
770:2008-12-14
648:2008-12-14
619:2013-01-21
594:2015-07-06
513:References
472:inductance
323:Hard disks
265:saturation
246:reluctance
170:coercivity
110:molybdenum
83:Properties
708:GB279549A
487:ductility
479:permalloy
468:bandwidth
455:inductive
419:permalloy
392:circuits.
380:electrons
295:cryogenic
248:path for
193:annealing
178:permalloy
94:16% iron,
844:Archived
434:ferrites
432:Ceramic
358:used in
305:Examples
197:hydrogen
151:Mumetal2
147:Mumetall
106:chromium
54:Mu-metal
32:nu metal
18:Mu metal
694:7196422
505:inside
441:History
423:Sendust
182:ductile
143:MuMETAL
128:silicon
714:
692:
682:
566:
541:
213:carbon
209:grains
149:, and
99:copper
58:nickel
690:S2CID
503:fuzes
130:, and
101:, and
69:alloy
64:soft
56:is a
680:ISBN
564:ISBN
539:ISBN
497:and
362:and
354:The
164:and
62:iron
672:doi
638:FAQ
343:LPs
275:kHz
108:or
104:2%
97:5%
79:.
864::
811:.
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688:.
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611:.
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521:^
421:,
285:.
271:RF
153:.
145:,
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773:.
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651:.
622:.
597:.
572:.
547:.
372:.
366:.
139:μ
112:.
60:–
34:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
