Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
  • G08B13/2408—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using ferromagnetic tags
  • G08B13/2411—Tag deactivation
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C45/00—Amorphous alloys
  • C22C45/04—Amorphous alloys with nickel or cobalt as the major constituent
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
  • G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/147—Alloys characterised by their composition
  • H01F1/153—Amorphous metallic alloys, e.g. glassy metals
  • H01F1/15316—Amorphous metallic alloys, e.g. glassy metals based on Co

Definitions

• the invention relates to an amorphous alloy for strip-shaped sensor elements with low saturation induction for use in anti-theft labels, magnetic field detectors or the like.
• Narrow and thin strips of a well soft magnetic material are required for security labels. So far, commercial strips made of both crystalline and amorphous material have been used. The usual dimensions are tape widths less than 3 mm, tape thicknesses less than 40 ⁇ m and label lengths from 50 to 100 mm, in some cases even less. It is important for the functioning of such strips that the material can be completely magnetized or re-magnetized with the smallest possible exciting magnetic fields. Due to the non-linearity of the magnetization curve of the strip when magnetic saturation is reached, then the magnetization in a corresponding receiver coil of an anti-theft system z. B. harmonics of the excitation frequency are generated, which are used to detect the strip and thus a possible thief.
• the field strength H s which is necessary to completely magnetize the strip, is essentially determined by the geometry of the strip (magnetic shear effect) and the magnetic anisotropy energy transverse to the strip direction.
• H s is the geometry of the strip (magnetic shear effect) and the magnetic anisotropy energy transverse to the strip direction.
• w is the width
• t is the thickness
• 1 is the length of the strip
• B s is the saturation induction
• H A is the magnetic anisotropy field.
• the factor ⁇ also depends, albeit only very weakly, on the strip geometry and can essentially be regarded as constant.
• the magnetic excitation field strength in the current systems must be about the order of magnitude or greater than the saturation field strength H s , if possible.
• H s saturation field strength
• z. B. to avoid false alarms by other ferromagnetic objects or for reasons of power requirements for the excitation field strength, to reduce unnecessary losses or heating, the excitation field strength should not be too large.
• the demagnetizing field in the strip direction is significantly reduced according to the equation. This has the desired effect that the magnetic stripe can be remagnetized in relatively small excitation fields and thus delivers the desired signal.
• the saturation field strength H s can be reduced further by making the anisotropy field H A almost disappear by special heat treatments.
• This is e.g. B. the case for magnetic material with an intrinsically rectangular magnetization loop, which is why such a material turned out to be particularly suitable in many cases.
• the invention has for its object to find an amorphous alloy with which, if necessary, the length of the strip-shaped sensor elements can be reduced in the sense of miniaturization, it must be ensured that the desired function can also be performed.
• This object is achieved according to the invention by the use of an amorphous, magnetostriction-free alloy with a saturation induction of B s ⁇ 0.5 T and good responsiveness in an annealing treatment in the magnetic field to achieve a remanence ratio of B r / B s > 0.6 .
• the present invention is based on the finding that for such special applications the saturation field strength H s can be achieved not only by reducing the cross section but also by reducing the saturation magnetization.
• the known, commercially available alloys in the field of application according to the invention all have a saturation magnetization B s of greater than 0.5 T.
• B s saturation magnetization
• EP-OS 0 121 694 shows that the saturation magnetization is far greater than 0.5 T, and it is noted that it is particularly advantageous if the saturation magnetization has a value equal to or greater than 1 T .
• a reduction in the saturation induction can always be achieved by dilution of known compositions by magnetically inactive atoms.
• alloys with low B s often no longer respond in the desired manner to heat treatment in the magnetic field.
• good responsiveness to heat treatment in the longitudinal field is required in order to achieve a Z-shaped loop with a required remanence ratio of B r / B s > 0.6.
• the element T Nb and this can be replaced by Mo, Cr, V, Zr, Ti, W in some cases up to 3 at% (based on the total alloy).
• u 4 to 10 at.%
• X 35 to 45 at.%
• Y 0 to 1
• z 21 to 23 at.%.
• the attached table shows the results of a series of alloys which have been subjected to heat treatment in the longitudinal field. For economic reasons, such a heat treatment should not take too long, ie be shorter than about 1 day and still achieve a remanence ratio B r / B s > 0.6.
• the table shows that the alloys 1 to 6 have a saturation induction in the desired range, but do not respond sufficiently to a heat treatment at all temperatures used here (ie, no desired remanence ratio B r / B s > 0.6 could be achieved ).
• Fe40 Ni40 B20 B s 1.0 T.
• alloys 7 to 11 are known, which respond well to heat treatment (B r / B s > 0.6 achievable), but which all have B s > 0.5 T and are out of the question for these desired applications.
• alloys 7 to 11 are suitable, which achieve both B s ⁇ 0.5 T and B r / B s > 0.6.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Electromagnetism (AREA)
• Automation & Control Theory (AREA)
• Computer Security & Cryptography (AREA)
• General Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Metallurgy (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Dispersion Chemistry (AREA)
• Power Engineering (AREA)
• Soft Magnetic Materials (AREA)
• Burglar Alarm Systems (AREA)

Applications Claiming Priority (2)

Publications (3)

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Cited By (4)

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Citations (4)

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• 1987
  • 1987-05-21 DE DE19873717043 patent/DE3717043A1/de not_active Withdrawn
• 1988
  • 1988-04-23 EP EP88106558A patent/EP0291726B1/fr not_active Expired - Lifetime
  • 1988-04-23 DE DE8888106558T patent/DE3881962D1/de not_active Expired - Fee Related
  • 1988-05-17 JP JP63118417A patent/JP3065085B2/ja not_active Expired - Lifetime
• 1990
  • 1990-05-15 US US07/523,176 patent/US5037494A/en not_active Expired - Lifetime

Patent Citations (4)

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