Rare earth permanent magnets are generally served in the focusing device of the particle beam in the accelerator, synchrotron and spectroradiometer. Rare earth permanent magnets may expose to radiation of γ-ray, neutron or other charged particles and tremendous amounts of cosmic rays are also existing in space. Actually, the energy of these cosmic rays can achieve 1020eV, and these all-pervasive high-energy rays will interact with magnetic material’s atoms, then caused lattice vibration and heat of magnet, thus lead to demagnetizing. Therefore, rare earth permanent magnets for undulator of high-energy nuclear field or propeller of aerospace field have high requirements in high-temperature resistance and anti-radiation performance.
It should be noted that some relevant researches have indicated that γ-ray irradiation basically not affects the magnetic properties of rare earth permanent magnets if magnet’s heat can be steady kept at room temperature. But in reality, permanent magnets cannot always remain at room temperature. According to the experimental data from Electron Energy Corporation (EEC), anti-radiation performance of Samarium Cobalt magnets are much better than Neodymium magnets. When neutron flux relatively low, the magnetic performance can be recovered after re-magnetized, and strong irradiation will cause permanent damage on the microstructure of Neodymium magnets, thus decrease its coercivity and remanence. In fact, irradiation damage is stemming from heat effect, not caused directly by metallurgical structural damage. The internal temperature of permanent magnets will rise with increasing neutron flux. Therefore, Neodymium magnet will lose its magnetism once internal temperature higher than its curie temperature. Sm(CoFeCuZr)x is the best choice to the space applications.
