Materials Composition of Retaining Magnet Assemblies

Hard ferrite (HF)

SrFe (Strontium ferrite).
Magnets made of hard ferrite (80% iron oxide) are made by sintering process.
Like all ceramic materials, these magnets are very hard and brittle and virtually non-machinable.
The magnetic adhesive force drops when the magnet is heated.

AlNiCo (AN)

Aluminium nickel cobalt.
Magnets made of AlNiCo (main constituents include aluminium, nickel, cobalt and iron) are made by sintering or casting process.
The material is very hard and tough, but can be redressed.
These magnets are used in applications in which the magnetic field is to remain as static and stable as possible; also under higher temperature fluctuations.

SmCo (SC)

Samarium cobalt.
Magnets made of SmCo (main constituents include samarium and cobalt) are made by sintering process.
The material is very hard and brittle and is virtually non-machinable.
The magnetic adhesive force drops when the magnet is heated.

NdFeB (ND)

Neodymium iron boron.
Magnets made of NdFeB (main constituents include neodymium, iron and boron) are made by sintering process.
The material is very hard and brittle and is virtually non-machinable.
This material delivers ultimate magnetic holding power.
The magnetic adhesive force drops when the magnet is heated.

Comparison of Magnet Materials:

Description Hard ferrite (HF) AlNiCo (AN) SmCo (SC) NdFeB (ND)
Pulling force good medium strong very strong
Max. working temperature* ~ 390°F (200°C) ~ 840 °F (450°C) ~ 390°F (200°C) ~ 175 °F (80°C)
Corrosion resistance very good very good good less good
Machineability not possible diamond cutting, grinding not possible not possible
Demagnetization capability moderate -
by demagnetizing fields
easy -
by demagnetizing fields
very difficult -
only by large demagnetizing fields
difficult -
only by large demagnetizing fields
Price very reasonable high very high reasonable

*The maximum temperature used is only a guide value, because it also depends on the dimensions of the magnet.