Reed Relays and
Electronics India Limited
Manufacturer of Reed Switches, Reed Sensors and Reed-based products
Reed Relays and Electronics India Limited Incorporated in 1971
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Magnet Information

In general, there are four families of magnets available commercially. Factors such as operating temperature, demagnetizing effects, field strength, environmental characteristics, and available space for movement need to be considered before selecting a magnet for a reed switch or reed sensor application. An overview of each of the families of magnets is given below. A list of our standard magnets is available here.

NdFeB

An NdFeB, or Neodymium Iron Boron magnet, is a type of rare earth magnet which is one of the strongest available commercially.

  • Highest energy product
  • Very high remanence and coercivity
  • Relatively low priced
  • Mechanically stronger
  • Some grades can be used up to 200°C
  • Not recommended in Hydrogen atmosphere
  • Bonded types can be machined but not tapped

SmCo

An SmCo or Semarium Cobalt magnet, it a also a type of rare earth magnet which is not as strong as NdFeB magnets but can withstand higher temperatures.

  • High energy product
  • Suitable for high performance applications
  • High resistance to demagnetization
  • Excellent thermal stability
  • High corrosion resistance
  • Most expensive magnet
  • Can be used up to 300°C
  • Prone to chipping – should not be used as a structure

AlNiCo

An AlNiCo or Aluminum Nickel Cobalt magnet, is a type of magnet have high coercivity, or resistance to loss of magnetism.

  • Cheaper than rare earth magnets
  • Highest working temperature of 550°C
  • Lowest temperature coefficient
  • Low coercivity when compared to other types
  • High induction levels

Ferrite

A Ferrite or hard ferrite ceramic magnet, is a type of magnet that is electrically non-conductive and generally low cost permanent magnets.

  • Brittle
  • Poor thermal stability
  • Cheapest of all types
  • Can be used up to 300°C
  • Needs grinding to meet tight tolerances
  • High corrosion resistance

Magnet Selection Guide

Depending on what a reed switch or reed sensor application demands, we have tabulated the properties of the four types of magnets in increasing order of magnitude. The most important property required should be looked at first and then subsequent ones, to get best results.

Low High
Cost Ferrite AlNiCo NdFeB SmCo
Energy Ferrite AlNiCo SmCo NdFeB
Operating Temperature NdFeB Ferrite SmCo AlNiCo
Corrosion Resistance NdFeB SmCo AlNiCo Ferrite
Resistance to Demagnetization AlNiCo Ferrite NdFeB SmCo
Mechanical Strength Ferrite SmCo NdFeB AlNiCo
Temperature Coefficient AlNiCo SmCo NdFeB Ferrite

Units Conversion Table

Property CGS Unit SI Unit Conversion Factor
Magnetic Flux Maxwell Weber 1 Weber = 108 Maxwell
Magneto-motive Force Gilbert Ampere-Turn 1 AT = 1.256 Gilbert
Magnetic Flux Density (B) Gauss Tesla 1 Tesla = 104 Gauss
Magnetic Field Strength (H) Oersted Ampere-Turn/Metre 1 AT/m = 0.0125663 Oersted
Magnet Performance (BHmax) MGOe Kilo-Joules/Metre3 1MGOe = 7.957 KJ/m3