Ultra-High Temperature Samarium Cobalt Magnets and Magnet Assemblies

Magnetic Properties      Demagnetization Curves

Since 1970, SmCo5 and Sm2Co17 magnets have been satisfying needs for magnets that reach operating temperatures up to 330°C. But when the operating temperature of these conventional magnets exceeds 330°C, their extrinsic demagnetization curves become nonlinear, characterized by a “knee” in the curve.

In 1995, the U.S. Air Force and other branches within the U.S. Department of Defense had described requirements for magnets capable of operating at temperatures greater than 400°C. In response to those needs, Electron Energy Corporation (EEC) has developed a new class of Sm2Co17 magnets for use at temperatures up to 550°C. These magnets have high-to-moderate energy product (BH)max, high intrinsic coercivity, Hci, and straight-line extrinsic demagnetization curves up to 550°C.

Our objective during the development of this new class of materials was to maintain a substantially linear extrinsic demagnetization curve at higher temperatures while maintaining the maximum possible energy product.

Accordingly, a new symbol (Tm) was introduced, which is defined as the maximum temperature at which the extrinsic demagnetization curve of a magnet is a straight line.

A straight-line extrinsic demagnetization curve is of value to designers of minimum volume and minimum weight devices. The straight-line curve is even more important for dynamic or highly loaded applications where high demagnetization forces are encountered. For optimum performance, a discrete magnet composition is required for each specific temperature, (Tm).

There is one area in which these ultra-high temperature magnets have already been successfully tested – space travel. In October 1998, NASA launched Deep Space 1, the first in a series of deep-space and Earth-orbiting missions conducted under the New Millennium Program designed to demonstrate new technologies in the environment of space.

During its highly successful primary mission, the satellite tested 12 advanced, high-risk technologies in space, including an ion-propulsion engine manufactured by Hughes Electron Dynamics using EEC’s high temperature magnets. In an extremely successful extended mission, Deep Space 1 encountered the comet Borrelly and returned the best images and other scientific data ever from a comet.