A COMPARISON OF MAGNETIC MATERIALS – AT A GLANCE

There are five types of magnet material that a magnet can be manufactured from:

1 - Neodymium iron boron (NdFeb)

Neodymium magnets are the most powerful magnets available (per unit volume) with the ability to attract 1,000 times their own weight. They have an elaborate manufacturing process of vacuum melting, milling, pressing and sintering.

These magnets can then sliced into smaller magnets or ground to tighter tolerances using diamond grinding tools. All neodymium magnets are plated to prevent rusting and are used wherever a very small size and maximum power is needed.

Strengths

Weaknesses

High magnetismLow operating temperatures
Ultra-high resistance to being demagnetisedPoor resistance to corrosion if the plating is damaged
High power to volume or weight ratio. 

 

2 - Alnico

Alnico is cast in a foundry. Patterns are used to make sand moulds and molten magnet material is poured into sand moulds. The patterns, tooling and high cost of Cobalt can make alnico magnets expensive. Alnico can also be manufactured using a sintering process to form smaller and more accurate magnets than those that are formed using a casting technique.

Strengths

Weaknesses

High operating temperatures

Low resistance to demagnetisation (pushing two magnets together in repulsion can permanently damage both of them)

Good corrosion resistanceHigh production cost
Long-term magnetic stability 

 

3 - Ceramic (Fe3O4)

Ceramic is manufactured using powder sintering technology and is sintered using exact size tooling into a range of industry standard sized discs, rings and block shapes. An industry sized block is a 150mm x 100mm x 25mm.

These blocks can then sliced into smaller magnets or ground to tighter tolerances. Ceramic are used extensively in loudspeakers and security systems industries.

Strengths

Weaknesses

Moderate operating temperatures

Low levels of magnetism mean that magnets have to be relatively large to be effective

High corrosion resistance, good magnetic stability 
Inexpensive 

 

4 - Samarium cobalt (SmCo)

Samarium Cobalt is manufactured using vacuum powder sintering technology and is sintered using special tooling techniques into standard disc, ring and block shapes.

These magnets can then be sliced into smaller magnets or ground to tighter tolerances using diamond grinding tools. Samarium cobalt is not as powerful as neodymium but it is still a rare earth high-power material. It offers a high performance per unit volume and is used in high-power applications where long term reliability is critical.

Strengths

Weaknesses

Moderately high magnetismHigh production costs
High resistance to being demagnetised 
Medium temperature resistance 
High resistance to corrosion 
Good power to weight ratio. 

 

5 - Magnetic rubber

Magnetic rubber is produced by heavily loading ceramic powder of barium or strontium base into a synthetic rubber or PVC matrix and either extruding to shape or calendaring into thin sheets. Magnetic rubber can be cut with scissors and can be supplied with adhesive backing, bright coloured vinyl facing and is easily cut into special shapes using form cutters.

Each magnet material has many grades and variations to provide a variety of slightly different magnetic properties. More details about different grades of each type of magnet can be found in the relevant section of our Tech Centre.

Strengths

Weaknesses

Flexible

Low magnetic flux density

Easy to cutLow max operating temperature
Good corrosion resistance 

The following details give a simple overview of the five Magnet Materials:

Type

Composition

Br (Gauss)

HC (Oesteds)

BH max (MG0e)

Density g/cm3

Max Operating Temp

Temp Coefficient

Neodymium
(Properties for common grade N42)

Mainly neodymium, iron and boron

13,0000 G 11,5000 Oe 42 MGOe7.4 g/cm3 80°C 0.11%

Alnico
(Properties for common grade Alnico 5)

Mainly aluminium, nickel, cobalt, iron

 12,500 G 640 Oe 5.5 MGOe 7.3g/cm3 500°C -0.02%

Ceramic
(Properties for common grade Ceramic 8)

 Ceramic materials and iron oxide (Fe2O3) 3,850 G 2,950 Oe 3.5 MGOe5g/cm3 180°C -0.2%

Samarium cobalt
(Properties for common grade Samarium 2:17)

Mainly samarium and cobalt11,000 G 9,700 Oe28 MGOe8.4 g/cm3 350°C 0.11%

Magnetic rubber
(Properties for common grade Y)

Strontium or barium powder and synthetic rubber or PVC 2,000 G1600 Oe 0.8 MGOe3.5 g/cm3 50°C 0.2%

 

  • Br = Volume of magnetism
  • Hc = Resistance to demagnetisation
  • BH max = Maximum energy product
  • Temperature coefficient = Percentage of magnetism lost for each degree Celsius rise in temperature but regained on cooling

 

CATERGORIES 

Educational Articles

Neodymium Magnet Information

Alnico Magnet Information

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