Alnico Magnet Material

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Alnico Magnetic Materials

Alnico magnets have the best temperature coefficients of any magnet material. Alnico magnets are a best choice in extremely high temperature applications.

Alnico magnets are Cast or Sintered.

Weaker Isotropic Alnico takes complex magnetic fields. Stronger Anisotropic Alnico has a fixed DoM axis.

Cast Alnico 5 is the most common grade of Alnico, with the LNG44 variant of Alnico 5 (Alcomax 3) being the most popular.

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Advantages & Disadvantages of Alnico Magnets

Advantages

Cast Alnico offers a near net shape. Cast Alnico can be produced to complex shapes with complex magnetic patterns.
Alnico Br as high as NdFeB at room temperature.
Can be used up to 450-550°C (842-932°F)
Least variation in magnetic output with temperature change of any magnetic material.
Can be cast in very large sizes.

Disadvantages

Sintered Alnico is usually limited to small to medium sizes and simpler shapes.
Low coercivity (Hci) making them easy to demagnetize.
Complex cast Alnico sometimes needs sand mold tooling which can be expensive if existing tooling is not available.

Typical applications for Alnico magnet materials

Very high temperature applications
Used in hot oils
Clamping
Motors and Generators
Mass spectrometers
Precision sensors and meters
Aerospace

Example

A company was using Alnico to operate a Mass Spectrometer but they were struggling to achieve the required magnetic field to detect the materials they were testing for.

The solution was to use a higher strength of Alnico magnet assembly and then deliberately use the low coercivity of Alnico to demagnetize it slightly to tune the magnetic field in the assembly air gap to the required field strength.

The thermal stability of the Alnico meant that the field would be stable enough for the entire operation of the unit.

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