What is the limit temperature of samarium cobalt magnets?

The Samarium cobalt magnets (SmCo) were often used as an option for extreme environments for its high-temperature resistance. But what is the limit temperature of samarium cobalt? This question becomes more and more important as the number of extreme application environments increases. The Curie temperature of ferromagnetic materials is usually the upper limit of the application temperature. Above this temperature, the magnet changes from a ferromagnetic state to a paramagnetic state, and no longer has strong magnetic characteristics. For example, the Curie temperature of 2:17 SmCo is about 820°C, and that of 1:5 SmCo is about 750°C. The composition and structure of the magnets are always different, the Curie temperature is slightly different, but it is generally in this range. As Figure 1 shown.

Figure 1. Curie temperature of different permanent magnet materials

However, in the actual application, SmCo magnets are prone to irreversible magnetic loss when the temperature is much lower than the Curie temperature. The maximum temperature (Tmax) of SmCo is limited by the temperature coefficient of coercivity and the working point caused by the different shape of the magnets. If the B-H curve in the second quadrant is used as a straight line as the judgment standard (Chen, JAP, 2000), the Tmax of the commonly used SmCo magnets does not exceed 350°C. As shown in Figure 2, the excellent magnetic properties of 32H magnet at 20 °C is Br≥11.3kGs, Hcj≥28kOe, Hk≥21kOe, and BHmax≥30.5kOe. However, the temperature coefficient β (20-350 °C) of its intrinsic coercivity Hcj is 0.042%, and its B-H curve is still difficult to maintain an absolute straight line in the second quadrant at 350 °C.

Figure 2, the temperature curve of 32H.

Hangzhou Magnet Power Co.Ltd has developed a series high temperature resistant SmCo magnets (T series) from 350 °C to 550 °C. As shown in Figure 3, these magnets are from the T350 with a Tmax of 350 °C to the T550 with a Tmax of 550 °C. For specific performance, please refer to the website link https://www.magnetpower-tech.com/t-series-sm2co17-smco-magnet-supplier-product/.This material is suitable for high temperature applications such as chemical industry, turbine and so on.