Exposing a magnet to high temperatures can decrease its strength or permanently damage its structure. Usually this happens at very high temperatures, but for certain neodymium magnets the threshold coul be as low as 80°C.
It’s not only about high heat evironments like engines or ovens, even a short exposure, maybe caused by an electric current or from friction, can lead to a loss of magnetization.
Standard Neodymium Magnets have a maximum working temperature of 80°C. Fortunately, there are 4 types of commercialy available magnetes that can withstand way higher temperatures: Alnico, SmCo, Ferrite and specifically treated Neodymium Magnets.
Which are the best Heat Resistant Magnets?
Alnico Magnets offer the highest temperature resistance among permanent magnets, up to 650 °C without incurring in any loss of performance. The only downside is their relatively low magnetic force, which is lower than Neodymium.
SmCo Magnets (Samarium-Cobalt Magnets) offer a good balance between heat resistance and attraction force. In fact, they are only slightly weaker than common Neodymium magnets, while boasting an excellent corrosion resistance and a max working temperature of 350 °C.
Ferrite Magnets are a good option at a competitive price, being also very resistant to corrosion, humidity and oxidation. They can withstand temperatures up to 250 °C.
Neodymium Magnets can be manufactured with specific treatments to increase their heat resistance. This is indicated by a letter in the name, after their grade: an “H” magnet is made to operate at temperatures of up to 120 °C, “SH” up to 150 °C, “UH” up to 180 °C, “EH” up to 200 °C.
Neodymium Magnets
Neodymium Magnets are the strongest commercially available magnets, but they are vulnerable to extreme heat.
There are Special Heat Resistant Neodymium Magnets marked by the acronyms M, H, SH, UH, EH. These letters, usually written before the grade of the magnet, indicate the maximum temperature a magnet can withstand without suffering damages. For example, a magnet with a threshold of 100 °C will be displayed as N35M. An “H” magnet can withstand temperatures of up to 120 °C, “SH” up to 150 °C, “UH” up to 180 °C, and “EH” up to 200°C. 80 °C is the standard limit for our Neodymium Magnets (no acronym in the product description).
You can find the maximum working temperature for each magnet in the “Additional Information” section of the product page.
If you want to know more about Neodymium Magnets here you can read our dedicated article:
Neodymium Magnets: The Complete Guide
Ferrite Magnets
Ferrite Magnets are strong and very resistant to high temperatures and corrosion. They don’t easily demagnetize and can be used up to 250°C without any loss in performance. These magnets are dark grey and their strength is slightly lower than Neodymium ones. They are also called raw magnets, hard ferrite magnets, ceramic magnets or ceramic permanent magnets. Compared to Neodymium, Alnico and SmCo magnets they are very cheap.
If you want to know more about Ferrite Magnets here you can read our dedicated article:
Ferrite Magnets: The Complete Guide
Samarium – Cobalt Magnets (SmCo)
Made with Samarium and Cobalt , these rare earth Magnets are very resilient for High Temperature Applications, and boast a working temperature of up to 350°C. The attraction force of SmCo alloys is higher than Ferrite, but slightly inferior than Neodymium, at least at room temperature. Above 150/180°C and in extremely cold conditions they outperform Neodymium Magnets.
Samarium Cobalt Magnets are resistant to corrosion and oxidation because they contain only traces or no Iron at all.
SmCo magnets are made by mixing and pressing Samarium and Cobalt powders with other elements in lesser concentration (hence the acronym SmCo). This process is called sintering. They can withstand very High Temperatures – up to 350°C, without risks of structural damage or demagnetization. They were the first rare-earth commercially available magnet and the strongest type of permanent magnet before the introduction of Alnico Magnets. Samarium Cobalt magnets are quite brittle and with low mechanical strength.
SmCo Magnets are usually classified based on the ratio of samarium to cobalt used during the manufacturing process:
SmCo5 – the ratio of samarium to cobalt is 1:5. Slightly weaker than its counterpat but with maximum restistance to corrosion.
Sm2Co7 – the ratio of samarium to cobalt is 2:7. The strongest version. Marginally susceptible to corrosion because contains traces of Iron.
Alnico Magnets
Alnico Magnets are the best performing magnets for High Temperature Applications, and boast a working temperature of up to 650 °C. The attraction force of Alnico is higher than Ferrite, but slightly inferior to Neodymium.
Exposing a magnet to high temperatures can decrease its strength or permanently damage its structure. For certain neodymium magnets this can happen at as low as 80°C. The maximum working temperature is displayed under “Max Temperature” in the Additional Information section of the product page.
Alnico magnets are made of an Iron alloy of Alluminium, Nickel, Cobalt and other elements in lesser concentration (hence the acronym Al-Ni-Co). They are produced via a melting process. They can withstand very High Temperatures – up to 650 °C, without risks of structural damage or demagnetization. They were the strongest type of permanent magnet before the introduction of modern rare-earth magnets (Neodymium).
They are the best choice for High Heat Applications, and retain useful magnetism even when heated to a bright red color. Their Curie Temperature is around 800 °C, meaning that the magnet permanently loses all of its magnetization only above the 800 °C threshold.
High temperatures and loss of magnetization
What temperature can a magnet withstand?
Standard Neodymium Magnets have a maximum working temperature of 80°C. This threshold is 250°C for Ferrite Magnets, 350°C for SmCo Magnets and 650°C for Alnico Magnets. There are also specially treated Neodymium Magnets with working temperatures above 80°C.
What is the working temperature of a magnet?
The working temperature is the maximum temperature a magnet can withstand for prolonged periods of time without incurring in a loss of performance, either temporary or permanent.
What is the Curie temperature of a magnet?
The Curie temperature is the temperature above which a magnet loses all of its magnetization permanently. In this case, the structure is compromised beyond repair and remagnetization is no longer possible. Standard neodymium magnets have a Curie temperature of 310 °C (340-350°C for special M, H, SH, UH, EH, TH magnets). The Curie temperature for Ferrite magnets is 450°C, for SmCo Magnets ranges from 700 to 800 °C while for Alnico Magnets is 700–850°C.
What happens if you heat a magnet above its maximum working temperature?
Heating a magnet above its maximum working temperature will cause a temporary or permanent loss of magnetization (adhesive force). The end result will change based on how much the heat exceeds the working or (eventually) the Curie temperature of the magnet.
Here are the possible scenarios:
Permanent loss of performance
If the heat reaches values higher than the maximum working temperature, the magnet is weakened permanently. Cooling it down may recover some magnetization, but some of the loss will be permanent.
Irreversible loss of magnetization
If the heat surpasses the Curie temperature, the structure of the magnet is altered permanently.
Important Notes
The shape and size of a magnet, together with the direction of magnetization (axial or diametrical, for example) can substantially change its heat tolerance.
Moreover, the time of exposure can make a difference for larger magnets. The outer part can reach critical temperatures while the core can be less impacted, resulting in an irregular magnetization.
If you want to know more about permanent magnets, other causes of loss of magnetization and proper magnets storage read our dedicated article:
Loss of Magnetization and Demagnetization of Permanent Magnets
Contact our technical team for further specifications about our magnets and an evaluation of your use case. If you store multiple magnets together, stack them together in piles. Avoid keeping strong magnets in close vicinity to one another. Permanent magnets are quite brittle, so strong impacts can chip or crack its structure, resulting in a loss of performance. Neodymium magnets are vulnerable to oxidation and corrosion, so exposure to water and humid environments should be avoided.
For further assistance about our products, technical support, products documentation and custom designed products, do not esitate to contact our team! We offer multilingual support by Mail, Chat or Phone.
