Coercivity by Magnet Type
Introduction to Magnetic Coercivity
Coercivity (coercive force), determines how well a magnet can resist external forces that would cause it to lose its magnetic properties. The forces that can demagnetise, or degauss a permanent magnet include; temperature, alternating currents and kinetic force. High coercivity is necessary for magnets that will be exposed to these forces.
Neodymium magnets, or NdFeB magnets, are very magnetically powerful magnets but they can become demagnetised in temperatures above 80C. This is where samarium cobalt and alnico magnets are useful because they have excellent resistance to demagnetisation forces.
All permanent magnets, (neodymium, samarium cobalt, alnico and ferrite) have a north pole and south pole. Facing two of the same poles repel the magnets and facing opposite poles attract (facing north and south poles).
Neodymium
(NdFeB)
Samarium Cobalt
(SmCo)
Aluminium Nickel Cobalt (Alnico)
Ferrite / Ceramic
(SrO-6 /Fe2O3)
Coercivity by Magnet Type
Coercivity of Neodymium Magnets
Neodymium magnets are the most magnetically powerful permanent magnets available. These magnets are the most popular magnets that we manufacture because their use-cases are absolutely endless. Not only are they very magnetically strong, but they can be manufactured into almost any shape which makes them incredibly versatile.
The coercivity of neodymium magnets is dependent on the grade you choose. Although many people understand the grades range from est N35 to N52, there are actually many more grades to choose from. If you see a letter after the number, for example, N45SH, the letters indicate the coercivity levels for that magnet. The number after the letter N (e.g. N45) refers to the magnetic power and the higher the number, the stronger the magnet. Below, you can see the heat tolerances for each grade of Neodymium.
No Letter – Max Temperature of 80 °C
N33, N35, N38, N40, N42, N45, N48, N50, N52, N55.
M – Max Temperature of 100 °C
N33M, N35M, N38M, N40M, N42M, N45M, N48M.
H – Max temperature of 120 °C
N30H, N33H, N35H, N38H, N40H, N42H, N45H, N48H.
SH – Max temperature of 150 °C
N30SH, N33SH, N35SH, N38SH, N40SH, N42SH, N45SH
UH – Max temperature of 180 °C
N33UH, N35UH, N38UH, N40UH, N42UH.
EH – Max temperature of 200 °C
N33EH, N35EH, N38EH.
AH – Max temperature of 230 °C
N33AH, N35AH.
This means that some neodymium magnets can withstand temperatures up to 230°C. This works by changing the material composition to include more heat-resistant materials. You can see a full datasheet of all of the neodymium grades by clicking the link below. Generally speaking, neodymium magnets with higher coercivity levels are capable of reaching lower magnetic power than ordinary neodymium magnets.
Coercivity of Samarium Cobalt Magnets
Samarium cobalt magnets are the second most magnetically powerful permanent magnets and have much better levels of coercivity than neodymium magnets. This means they can withstand extreme temperatures and other demagnetization forces without losing magnetism.
We often find people using samarium cobalt magnets in machinery and engines where the environment gets hot. We’ve also known people to use samarium cobalt magnets in ovens. There are many different grades that withstand high temperatures and you can see them below.
Max Temperature of 250 °C
SC-1615, SC-1819, SC-2019, SC-2219, SC-2416
Max Temperature of 300 °C
SC-2228, SC-2428
Max Temperature of 350 °C
SC-2618, SC-2826, SC-3018 and SC-3215.
This means that some grades of samarium cobalt magnets can withstand temperatures as high as 350°C. You can see all of the magnetic properties of samarium cobalt magnets here.
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