MINIATURE RARE EARTH & AlNiCo MAGNETS

For your custom magnet order provide:

• Type/Material: AlNiCo, Sintered or Bonded NdFeB (Neodymium), Samarium Cobalt, Ferrite/Ceramic
• Magnetic Performance: Grade
• Mag Direction: Axial, Radial. The most common is Match Radial.
• Shape: most common are cylinder, block, disc, ring, segment
• Coatings: NiCuNi, zinc, black epoxy, silver, gold, passivation, phosphate
• Quantity

These magnets, made from alloys of rare-earth elements, are the strongest type of permanent magnets. Neodymium and samarium-cobalt are the two types of rare-earth magnets.

Neodymium (NdFeB)

Neodymium magnets are the strongest and most affordable of the rare-earth permanent magnets. They are an alloy of neodymium, iron, boron and other trace elements. While having the highest magnetic field strength, they also provide a high rating for remanence, coercive force, magnetic energy and performance/cost ratio.

Bonded Neodymium (NdFeB)

Bonded NdFeB magnets are made by mixing fast-hardened NdFeB powder and a thermoplastic bonding agent and then generally formed by injection molding. This process results in high dimensional accuracy and is suitable for mass production. Due to the high content of polymer binder, the magnet has strong resistance and does not require surface coating protection. Complex shapes can be achieved through this process.

Bonded NdFeB are less expensive than sintered neodymium as the manufacturing has fewer processes and they are simpler. However, the magnetic performance is relatively low and the highest performance of the bonded magnet is only one-fifth of the sintered magnet. This magnet is suitable for some thin, small and irregular products

Sintered Neodymium (NdFeB)

Sintered neodymium uses a powder metallurgy process. The material is hard and brittle, making it difficult to process. It results in high loss during processing, high cost, poor dimensional accuracy, and poor corrosion resistance. Generally only blanks are produced and then through mechanical processes such as wire cutting, slicing, grinding, etc. the final shapes are formed. Vulnerable to oxidation and corrosion, sintered neodymium magnets generally have surface treatments applied to provide protection. In most cases a Nickel-Copper-Nickel plating provides robust protection.

Sintered neodymium magnets are more magnetic than the bonded neodymium and are more widely used. Applications range from electronics and motors, to electrical appliances, loudspeakers and filters.

Samarium-Cobalt (SmCo)

Samarium-Cobalt magnets are a rare-earth permanent magnet made of Samarium, Cobalt and other metal materials (SmCo5). They are extremely resistant to demagnetization. Due to a higher Curie temperature than NdFeB magnets, SmCo magnets are used in applications where high field strength is needed at high operating temperatures. They can be safely used at temperatures up to 500°F.

Samarium-Cobalt magnets have a strong resistance to corrosion and oxidation and generally do not require electroplating. Due to their molecular structure, sintered samarium-cobalt magnets are more fragile and prone to chipping and cracking and may fracture when subjected to thermal shock.

Applications: sensors, reed switches, audio equipment, electrodynamic bearings, MRI scanners, magnetically coupled pumps, motors and generators, magnetic bearings, medical devices, and industrial uses including maintaining product purity, equipment protection, and quality control.

AlNiCo Magnets are composed of aluminum, nickel and cobalt and are primarily used in technical applications where temperature stability is critical. They are one of the most stable magnets if they are handled properly.

The advantages of AlNiCo magnets are high remanence and low-temperature coefficient. Having high residual induction, they are also corrosion resistant. While no surface treatments are required, AlNiCo magnets can easily be plated. They are the only magnets that have useful magnetism even when heated red-hot. AlNiCo magnets are electrically conductive, unlike ceramic magnets.

There are two types of AlNiCo magnets, sintered and cast. Generally, cast-AlNiCo magnets can be produced in a variety of shapes and sizes while sintered-AlNiCo magnets are generally smaller in size and higher in precision. The magnetic properties of sintered-AlNiCo are slightly lower than that of cast-AlNiCo magnets. Cast-AlNiCo permanent magnets enjoy the lowest reversible temperature coefficient, and their working temperature can be as high as 600 deg C.

Applications: sensors, electric motors, meters, and for specialized holding/high-temperature applications.

Ferrite magnets, also known as ceramic magnets contain iron oxide in a ceramic composite and have the advantage of being able to be pressed into various shapes without significant machining. Ferrite magnets are resistant to corrosion and are not electrically conductive. They can resist the demagnetization of external magnetic fields. Ferrite magnets are fragile and can’t be used in machinery that is under great pressure or bending. Maximum operating temperature 572°F. With a medium intensity magnetic field, they are not suitable for applications requiring strong magnetic field.

Ferrite compounds are low cost and are typically used where price, rather than size or mass, is the primary driver.

Ferrites can be divided into two classes based on their resistance to being demagnetized.

Hard Ferrites have high coercivity so are difficult to demagnetize. They are used in applications such as refrigerator magnets, loudspeakers, and small electric motors.

Soft Ferrites have low coercivity, so they can easily change their magnetization and act as conductors of magnetic fields. They are used in the electronics industry to make efficient magnetic cores called ferrite cores for high-frequency inductors, transformers and antennas.

Residual Induction (Br) or remanence is a measurement of strength of the magnetic field.

• Measured in unit of Gauss.

Coercive Force (Hc) or coercivity is a measurement of resistance to becoming demagnetized.

• Measured in units of Oersteds.

Maximum Energy Product (BHmax) is measurement of density of magnetic energy to indicate volume of

• Magnet material required to project a given level of magnetic flux.
• Measure in units of Gauss-Oersteds.