Temperature Effects On Permanent Magnets

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While permanent magnets are designed to retain their magnetic properties over a wide range of temperatures, their strength can still be affected by temperature changes. As a general rule, the strength of a permanent magnet decreases as the temperature increases. This is because the magnetic properties of the material change as it is heated, leading to a decrease in its magnetic strength.

At temperatures above the maximum operating temperature of a permanent magnet, the magnet will experience a permanent loss of its magnetic properties. This means that if the magnet is cooled back to its original temperature, its magnetic strength will not be fully restored and weaker than before it was heated.

At temperatures between the Curie temperature (the theoretical maximum working temperature of a magnet) and the maximum operating temperature, the magnet will experience reversible or irreversible loss of its magnetic properties depending on the specific temperature range and the material it is made of. This means that if the magnet is cooled back to its original temperature, its magnetic strength may not be fully restored.

Therefore, it is important to understand the concepts of Curie temperature and maximum operating temperature when considering using permanent magnets in different applications.

What Is The Curie Temperature?

The Curie temperature, also known as the Curie point or magnetic transition temperature, is the temperature at which a material changes from being ferromagnetic (able to be magnetized) to paramagnetic (unable to be magnetized).

For permanent magnets, the Curie temperature is the temperature at which the magnet begins to lose its magnetic properties permanently.

The Curie temperature is typically specific to a particular material and can vary depending on the composition and structure of the material. Materials with a high Curie temperature are more resistant to losing their magnetic properties due to temperature changes and are more suitable for permanent magnets.

For example, the Curie temperature of a neodymium magnet is around 310 to 390 degrees Celsius (590 to 734 degrees Fahrenheit). This means that if a neodymium magnet is heated above this temperature, it will lose its magnetic properties permanently.

What Is The Maximum Working Temperature?

The maximum working temperature of a permanent magnet is the highest temperature at which it can be used without experiencing significant loss of its magnetic properties.

The maximum working temperature of a permanent magnet is typically lower than its Curie temperature, which is the temperature at which the magnet begins to lose its magnetic properties permanently.

The maximum working temperature of a permanent magnet can vary depending on the type of magnet and the material it is made of. For example, the maximum working temperature of a neodymium magnet is typically between -40 and 80 degrees Celsius (-40 to 176 degrees Fahrenheit). If a neodymium magnet is used at temperatures above its maximum working temperature, it may begin to lose its magnetic strength, which can affect its performance.

It’s important to note that the Curie temperature and maximum working temperature of a permanent magnet can be affected by factors such as the composition of the magnet material and the presence of impurities or defects. External factors, such as the presence of an external magnetic field or the application of mechanical stress, can also influence the maximum working temperature.

Curie Temperature &Max Working Temperature Table

The Curie temperature of a magnetic material is the theoretical maximum working temperature at which the material can be used. The higher the Curie temperature, the higher the maximum working temperature of the material will be and the better the temperature stability. This is because the material’s magnetic properties are less likely to be affected by temperature changes when the Curie temperature is higher.

It’s important to note that the Curie temperature is not the same as the maximum operating temperature, which is the highest temperature at which a magnet can be used without experiencing permanent loss of its magnetic properties. The maximum operating temperature will typically be lower than the Curie temperature and will depend on the specific composition and structure of the magnet.

Some common magnetic materials and their corresponding Curie temperatures and maximum operating temperatures are listed below:

Magnet Types Grade Curie Temperature/°CMaximum Working
Temperature/°C
Sintered NdFeBN310°C80°C
Sintered NdFeBM340°C100°C
Sintered NdFeBH340°C120°C
Sintered NdFeBSH340°C150°C
Sintered NdFeBUH350°C180°C
Sintered NdFeBEH350°C200°C
Bonded NdFeB310-340°C100-150°C
SmCo5700-750°C250°C
Sm2Co17800-850°C300-350°C
AlnNiCo750-850°C450-550°C
Ferrite>450°C250°C

How Does Temperature Affect Different Types Of Permanent Magnets?

There are several differences in how temperature can affect the performance of different types of permanent magnets. Some general trends include:

Neodymium Magnets:

These magnets are generally more sensitive to temperature changes than other magnets.

They tend to experience reversible loss of their magnetic properties at temperatures below their Curie temperature, around 310 to 390 degrees Celsius (590 to 734 degrees Fahrenheit).

They may also experience irreversible loss of their magnetic properties at temperatures above their Curie temperature but below their maximum operating temperature, typically between -40 and 80 degrees Celsius (-40 to 176 degrees Fahrenheit).

SmCo Magnets:

These magnets are generally more resistant to temperature changes than neodymium magnets, but are still sensitive to temperature changes.

They tend to experience reversible loss of their magnetic properties at temperatures below their Curie temperature, around 700 to 800 degrees Celsius (1292 to 1472 degrees Fahrenheit).

 They may also experience irreversible loss of their magnetic properties at temperatures above their Curie temperature but below their maximum operating temperature, typically between -40 and 200 degrees Celsius (-40 to 392 degrees Fahrenheit).

Alnico Magnets:

These magnets are generally less sensitive to temperature changes compared to neodymium magnets.

They tend to experience reversible loss of their magnetic properties at temperatures below their Curie temperature, around 730 to 770 degrees Celsius (1346 to 1418 degrees Fahrenheit).

They may also experience irreversible loss of their magnetic properties at temperatures above their Curie temperature but below their maximum operating temperature, typically between -40 and 550 degrees Celsius (-40 to 1022 degrees Fahrenheit).

Ferrite Magnets:

These magnets are generally less sensitive to temperature changes compared to neodymium magnets.

They tend to experience reversible loss of their magnetic properties at temperatures below their Curie temperature, around 550 to 700 degrees Celsius (1022 to 1292 degrees Fahrenheit).

They may also experience irreversible loss of their magnetic properties at temperatures above their Curie temperature but below their maximum operating temperature, typically between -40 and 150 degrees Celsius (-40 to 302 degrees Fahrenheit).

Conclusion

By understanding a magnet’s Curie temperature and maximum operating temperature, you can ensure that it is used within its recommended temperature range and avoid potential damage or performance issues. It’s always important to consult the manufacturer’s specifications for the specific Curie temperature and maximum operating temperature of a magnet to ensure that it is used within its recommended temperature range.

Are you in need of high-quality magnets for your business or personal use? Look no further than JDA Magnet Factory! Our team of experts is dedicated to providing you with the best possible service and support to help you find the perfect magnets for your application.

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