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Rare-Earth Magnets

Neodymium magnets are the strongest type of permanent magnet currently made. They are amazingly powerful for their size and have innumerable uses. MAGCRAFT® brand magnets are sold exclusively through National Imports LLC and its authorized distributors. The MAGCRAFT® line of permanent magnets, packaged in the MAGPAK™ system are composed of licensed grade 40 neodymium iron boron magnetic material and are plated in nickel-copper-nickel for a shiny corrosion resistant finish. All MAGCRAFT® brand magnets are licensed for use worldwide except in Japan.

Neodymium Magnet Types

Rare earth magnets are magnets composed of alloys of the Lanthanide group of elements. The two Lanthanide elements most prevalent in the production of permanent magnets are Neodymium and Samarium. There are numerous alloy formulations of rare earth magnets covered under many different patents but the most common commercial varieties are Neodymium-Iron-Boron (NdFeB) and Samarium Cobalt (SmCo).

Rare earth magnets are magnets composed of alloys of the Lanthanide group of elements. The two Lanthanide elements most prevalent in the production of permanent magnets are Neodymium and Samarium. There are numerous alloy formulations of rare earth magnets covered under many different patents but the most common commercial varieties are Neodymium-Iron-Boron (NdFeB) and Samarium Cobalt (SmCo).

There are two types of neodymium magnets commonly produced commercially: sintered and bonded.

Sintered Magnets

Sintered magnets are made from dry granules of elemental materials which are compacted under pressure in a metal die and then heated at high temperature to fuse the granules together. Sintered rare earth magnets are subjected to a magnetic field during the manufacturing process to orient the magnetic domains in the material. The magnetic orientation of sintered neodymium magnets is fixed during processing and cannot be changed later. This type of magnetic material is known as anisotropic.

The resulting material from the sintering process has similar physical properties to ceramic materials. They are hard and brittle, which makes them inappropriate for applications where they will be subject to shock. Sintered neodymium magnets have the highest energy product of any permanent magnetic material. Because sintered neodymium magnets can provide a strong magnetic field in a small size, they have revolutionized modern electronics allowing for the miniaturization of many electronic components such as motors and speakers. This has led to highly portable electronic devices such as cell phones and tablet computers.

Bonded Magnets

Bonded magnets are made from magnetic metal powder mixed with a polymer. The components are then cast or extruded into a final shape. Bonded magnets can be flexible depending upon what polymer is used in the production. Bonded magnets do not have a fixed magnetic orientation so they can be magnetized in complex patterns with many poles. This type of magnetic material is known as isotropic. Unfortunately, bonded neodymium magnets are much weaker than sintered neodymium magnets, which limits their application.

Magnet Grades and Properties

In addition to their physical characteristics, magnets are most commonly described by their magnetic characteristics. The most widespread classification of magnets is by grade. Grade is a combined identifier of the Maximum Energy Product and the Heat Tolerance of a magnet. To complicate matters more, the Maximum Energy Product is a combined measure of the Residual Flux Density and Coercive Force of a magnet. For the layperson, the Residual Flux Density can be thought of as a measure of magnetic strength. The Coercive Force is a measure of how difficult it is to demagnetize a magnet. Simply put, the higher the Maximum Energy Product, the "stronger" the magnet.

The Heat Tolerance is simply the highest temperature that a magnet can operate at without it permanently losing its magnetism. All magnetic materials will have lower magnetic force as their temperature increases but if you do not exceed their temperature rating they will return to normal as you return the temperature to normal.

The grade of a magnet is expressed as a one or two digit number with letters before or after the number to specify the heat tolerance. Examples:

  • Grade N40
    • N - Normal Temperature Grade (Maximum Working Temperature 80 Deg Celsius)
    • 40 - Maximum Energy Product 40 MGOe
  • Grade 35EH
    • 35 - Maximum Energy Product 35 MGOe
    • EH - EH Temperature Grade (Maximum Working Temperature 200 Deg Celsius)

Neodymium Magnet Coatings

The composition of neodymium magnets has improved over the years to reduce their susceptibility to oxidation but they are predominately made out of iron and neodymium. Both of these material will oxidize. There are various coatings available to reduce their susceptibility to oxidation. Nickel-Copper-Nickel plating has excellent corrosion resistance and durability as well as providing a clean and shiny appearance. In addition to NiCuNi coating, neodymium magnets can be coated in:

  • Nickel (Ni);
  • Epoxy;
  • inc (Zn);
  • Gold (Au);
  • Silver (Ag);
  • Tin (Sn);
  • Parylene C;
  • Uncoated.

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