There are a couple of choices of magnetic materials to consider when choosing a magnetic separator; ceramic and rare earth. Both of these are permanent magnets and will retain their full magnetic strength losing approximately ½ of 1% per 100 years if not subjected to physical abuse or temperatures that exceed their limitations. Almost all magnetic separators are offered in either ceramic or rare earth. The application typically dictates which is the proper choice of materials.
The magnetic strength of the raw magnetic material is measured in megagauss oersteds (MGO). This number will change as the magnet is integrated into a piece of separation equipment. By manipulating the north and south magnetic poles on the magnets thru placement and the use of steel pole pieces or back plates, the magnetic field is enhanced and directed into the product flow area for optimum separation. These materials are brittle and cannot be used as a structural component in a design. The actual magnetic material is secured within a stainless steel enclosure.
Magnetic Materials Used in Puritan Permanent Type Separation Products
Rare Earth Magnets
There are two types of rare earth magnets used in magnetic separators, Neodymium-Iron-Boron and Samarium Cobalt. Both are typically more expensive than ceramic, but provide a much higher MGO allowing for greater separation of ferrous fines. The term “rare earth” comes from the Neodymium and Samarium classification in the Lanthanides section of the Periodic Table of Elements.
Neodymium-Iron-Boron – This is the most commonly used rare earth material. The mills that produce this material are continually working on increasing the MGO. Currently the MGO for Neodymium-Iron-Boron used in separation magnets is between 45 and 50. The range in strength is relative to the size and shape of the material being used due to limitations in the manufacturing process. The maximum working temperature is up to 300 degrees F.
Samarium Cobalt – This material is more expensive than the Neodymium-Iron-Boron and has a lower MGO value, between 24-28. However, Samarium Cobalt does offer higher working temperatures up to 575 degrees F.
Composition and Manufacturing Process:
Two types of rare earth materials are available. The first type Samarium Cobalt, consists of Samarium ,Cobalt, and Iron. The second and more commonly used is Neodymium. This is composed of Neodymium, Iron, and Boron. The term "rare earth magnet" comes from Neodymium and Samariums classification in the lanthanides (rare earth) section of the periodic table of elements.
The composite materials of these magnets are melted together and then milled into a powdered form. This material is then dry pressed into the desired shape while a magnetic field is applied to orient the molecules. The final step includes sintering, being ground to the required dimension and magnetizing. | 
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