256:, 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.
27:
35:
435:
478:. 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
289:
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.
701:
218:
208:
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.
450:
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
425:
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.
245:
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
463:
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.
130:) which represents permeability in physics and engineering formulas. A number of different proprietary formulations of the alloy are sold under trade names such as
498:. Telcon Metals Ltd. abandoned the trademark "MUMETAL" in 1985. The last listed owner of the mark "MUMETAL" is Magnetic Shield Corporation, Illinois.
832:
699:, "New and improved magnetic alloys and their application in the manufacture of telegraphic and telephonic cables", issued 1927-10-27
672:
556:
531:
252:
The effectiveness of mu-metal shielding decreases with the alloy's permeability, which drops off at both low field strengths and, due to
38:
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.
233:
Mu-metal is a soft magnetic alloy with exceptionally high magnetic permeability. The high permeability of mu-metal provides a low
866:
797:
773:
146:
841:
622:
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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
456:
337:
249:
around the shielded area. Thus, the best shape for shields is a closed container surrounding the shielded space.
447:
861:
442:
Mu-metal was developed by
British scientists Willoughby S. Smith and Henry J. Garnett and patented in 1923 for
314:, which have mu-metal backings to the magnets found in the drive to keep the magnetic field away from the disk.
521:
470:, the first high-permeability alloy used for cable compensation, whose patent rights were held by competitor
173:, malleable and workable, allowing it to be easily formed into the thin sheets needed for magnetic shields.
856:
348:
181:
651:
Daniels, Ryan J.; McIntyre, Timothy; Kisner, Roger; Killough, Stephen; Lenarduzzi, Roberto (April 2015).
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189:
61:
479:
829:
105:
More recently, mu-metal is considered to be ASTM A753 Alloy 4 and is composed of approximately
352:
253:
246:
150:
678:
653:"Design and implementation of a Hall Effect sensor array applied to recycling hard drive magnets"
459:
and slowed signaling speed to 10–12 words per minute. The bandwidth could be increased by adding
378:
327:
324:, which have mu-metal shields to prevent stray magnetic fields from deflecting the electron beam.
242:
668:
552:
527:
390:
331:
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64:, which is used for shielding sensitive electronic equipment against static or low-frequency
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487:
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308:, which are built with mu-metal shells to prevent them from affecting nearby circuitry.
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when used in AC magnetic circuits. Other high-permeability nickel–iron alloys such as
34:
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270:: ordinary conductive metal sheets or screens which are used to shield against
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is used similarly in some transformers as a cheaper, less permeable option.
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311:
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have similar magnetic properties; mu-metal's advantage is that it is more
368:
185:
94:
76:
Mu-metal has several compositions. One such composition is approximately
20:
298:
Mu-metal is used to shield equipment from magnetic fields. For example:
597:
411:
170:
116:
201:
87:
46:
402:
Other materials with similar magnetic properties include Co-Netic,
474:. Mu-metal was developed by adding copper to permalloy to improve
455:
to the cable, causing distortion of the signal, which limited the
433:
216:
57:
33:
25:
491:
50:
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so that it saturates at low magnetic fields. This gives it low
749:"150 Years Of Industry & Enterprise At Enderby's Wharf"
572:
753:
History of the
Atlantic Cable and Undersea Communications
330:, which have a mu-metal case to reduce interference when
30:
Assortment of mu-metal shapes used in electronics, 1951
192:
about 40 times. The annealing alters the material's
737:, filed January 10, 1924, granted September 8, 1925
733:Willoughby Statham Smith, Henry Joseph Garnett,
721:, filed January 10, 1924, granted April 27, 1926
717:Willoughby Statham Smith, Henry Joseph Garnett,
523:Introduction to Magnetism and Magnetic Materials
278:materials can also expel magnetic fields by the
115:small amounts of various other elements such as
406:, supermumetal, nilomag, sanbold, molybdenum
8:
798:"Trademark Status & Document Retrieval"
774:"Trademark Status & Document Retrieval"
551:(64th ed.). CRC Press. p. E-108.
414:, M-1040, Hipernom, HyMu-80 and Amumetal.
371:, for example, photoelectron spectroscopy.
466:Telcon invented mu-metal to compete with
200:and removing some impurities, especially
204:, which obstruct the free motion of the
126:The name came from the Greek letter mu (
515:
513:
511:
507:
629:. Magnetic Shield Corp. Archived from
438:Mu-metal submarine cable construction
7:
385:Fluxgate magnetometers and compasses
229:, from a 1945 electronics magazine
14:
842:Info about using mu metal shields
549:Handbook of Chemistry and Physics
367:for experiments with low-energy
262:magnetic fields above about 100
188:atmosphere, which increases the
328:Magnetic phonograph cartridges
122:12~15% iron for the remainder.
1:
623:"Magnetic Fields and Shields"
180:after they are in final form—
482:(particularly shielding for
883:
665:10.1109/SECON.2015.7132879
526:. CRC Press. p. 354.
448:submarine telegraph cables
338:Magnetic resonance imaging
18:
598:"Mu Metal specifications"
176:Mu-metal objects require
604:. Nick Murby. 2009-03-25
602:Shielding Specifications
377:circuits and especially
241:, leading to its use in
19:Not to be confused with
867:Ferromagnetic materials
184:in a magnetic field in
145:Mu-metal typically has
547:Weast, Robert (1983).
439:
387:as part of the sensor.
349:magnetoencephalography
230:
39:
31:
747:Green, Allen (2004).
520:Jiles, David (1998).
437:
359:Photomultiplier tubes
221:Mu-metal shields for
220:
190:magnetic permeability
147:relative permeability
37:
29:
480:electronics industry
247:magnetic field lines
830:Zero gauss chambers
825:Mu-Metal Properties
353:magnetocardiography
266:can be shielded by
151:magnetic anisotropy
835:2013-02-17 at the
490:), as well as the
440:
379:Josephson junction
231:
157:, giving it a low
40:
32:
731:US Patent 1552769
715:US Patent 1582353
674:978-1-4673-7300-5
657:SoutheastCon 2015
558:978-0-8493-0463-7
533:978-0-412-79860-3
488:cathode-ray tubes
398:Similar materials
391:Proximity sensors
320:used in analogue
318:Cathode-ray tubes
223:cathode-ray tubes
194:crystal structure
163:hysteresis losses
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659:. pp. 1–6.
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472:Western Electric
416:Electrical steel
393:(inductive type)
340:(MRI) equipment.
334:are played back.
243:magnetic shields
155:magnetostriction
16:Trademark, alloy
882:
881:
877:
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875:
873:
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862:Magnetic alloys
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837:Wayback Machine
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375:Superconducting
365:Vacuum chambers
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280:Meissner effect
276:Superconducting
272:electric fields
268:Faraday shields
225:(CRTs) used in
215:
206:magnetic domain
196:, aligning the
74:
66:magnetic fields
60:with very high
24:
17:
12:
11:
5:
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819:External links
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802:tsdr.uspto.gov
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778:tsdr.uspto.gov
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739:
735:Magnetic Alloy
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719:Magnetic Alloy
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579:. Josh Wickler
573:"MuMetal Home"
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496:magnetic mines
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303:Electric power
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286:temperatures.
282:, but require
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178:heat treatment
124:
123:
120:
113:
112:5% molybdenum,
110:
103:
102:
91:
84:
81:
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70:
15:
13:
10:
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857:Nickel alloys
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633:on 2008-12-18
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55:ferromagnetic
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805:. Retrieved
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781:. Retrieved
777:
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757:. Retrieved
755:. FTL Design
752:
742:
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718:
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691:
656:
646:
635:. Retrieved
631:the original
626:
617:
606:. Retrieved
601:
592:
581:. Retrieved
577:mu-metal.com
576:
567:
548:
542:
522:
484:transformers
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441:
420:
401:
306:transformers
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144:
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125:
104:
75:
62:permeability
42:
41:
453:capacitance
446:loading of
404:supermalloy
213:Application
109:80% nickel,
80:77% nickel,
851:Categories
807:2017-07-28
783:2017-07-28
759:2008-12-14
637:2008-12-14
608:2013-01-21
583:2015-07-06
502:References
461:inductance
312:Hard disks
254:saturation
235:reluctance
159:coercivity
99:molybdenum
72:Properties
697:GB279549A
476:ductility
468:permalloy
457:bandwidth
444:inductive
408:permalloy
381:circuits.
369:electrons
284:cryogenic
237:path for
182:annealing
167:permalloy
83:16% iron,
833:Archived
423:ferrites
421:Ceramic
347:used in
294:Examples
186:hydrogen
140:Mumetal2
136:Mumetall
95:chromium
43:Mu-metal
21:nu metal
683:7196422
494:inside
430:History
412:Sendust
171:ductile
132:MuMETAL
117:silicon
703:
681:
671:
555:
530:
202:carbon
198:grains
138:, and
88:copper
47:nickel
679:S2CID
492:fuzes
119:, and
90:, and
58:alloy
53:soft
45:is a
669:ISBN
553:ISBN
528:ISBN
486:and
351:and
343:The
153:and
51:iron
661:doi
627:FAQ
332:LPs
264:kHz
97:or
93:2%
86:5%
68:.
853::
800:.
776:.
751:.
677:.
667:.
655:.
625:.
600:.
575:.
510:^
410:,
274:.
260:RF
142:.
134:,
810:.
786:.
762:.
685:.
663::
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611:.
586:.
561:.
536:.
361:.
355:.
128:μ
101:.
49:–
23:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
