Magnet

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Description

A a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets (Wikipedia 2019). Magnets can include the elements Iron, Nickel and Cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestones. Ferrous magnets of varying strength can be useful in storage and support applications. Rare earth magnets, such as neodymium or samarium-cobalt, are super-strong materials whose use is being explored for temporary, yet attachment of art, frames, mounts and supports.

Applications

  • Magnetic mounts: Detailed information on the AIC Wiki.
  • Magnetic recording materials (disks and tapes)
  • Magnetic identification strips

Risks

  • Rare earth magnets are extremely strong. Handle with caution as they can fly together and pinch fingers and art (AIC Wiki).
  • Rare earth magnets are brittle and subject to corrosion so they are usually plated or coated.

Physical and Chemical Properties

Magnet Composition preparation Magnetic field strength (BR) Resistance to being demagnetized (HCI) Density of Magnetic field (B.Hmax) Demagnetization temp (TC)
Nd2Fe14B sintered 1.0–1.4 750–2000 200–440 310–400
Nd2Fe14B bonded 0.6–0.7 600–1200 60–100 310–400
SmCo5 sintered 0.8–1.1 600–2000 120–200 720
Sm(Co,Fe,Cu,Zr)7 sintered 0.9–1.15 450–1300 150–240 800
Alnico sintered 0.6–1.4 275 10–88 700–860
Sr-ferrite sintered 0.2–0.4 100–300 10–40 450
Iron (Fe) bar magnet annealed ? 800 ? 770

Resources and Citations

  • Gwen Spicer, Magnetic Mounting Systems for Museums & Cultural Institutions book
  • G. Spicer “Ferrous Attractions: The Science Behind the Conservator’s Magic” Journal of the American Institute for Conservation (JAIC) vol. 55:2 (2016)
  • Wikipedia: Website (Accessed May 2019)
  • Wikipedia: Website (Accessed 11/2020)

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