Radiation Effects in Rare-Earth Permanent Magnets

Abstract

Nd-Fe-B and Sm-Co permanent magnets have been irradiated with fission neutrons and gamma rays. Irradiated samples were periodically removed for room temperature measurements of the open-circuit remanence. Hysteresis loops were measured before and after irradiation. For neutron irradiation, two Nd-Fe-B magnets showed a rapid loss of remanence, while a third magnet from another manufacturer decayed more slowly, suggesting that the radiation hardness of Nd-Fe-B magnets may depend on microstructural details. Irradiation in the Omega West Reactor at Los Alamos with fast neutrons caused the fast-decay samples to have an Wtial loss of remanence of 1% for irradiation at 350 K to a fluence of 1015 n/cm2. Both SmCo5 and Sm2Co17 magnets showed excellent resistance to radiatifg-induied loss of remanence for neutron irradiation to a fluence of 2.6×1018 n/cm2. Results for gamma radiation showed no loss of remanence for a dose of about 49 Mrad using a 60Co source. Possible mechanisms for radiation-induced loss of magnetic properties are discussed.

Enhancement of magnetization of Mg–Mn nanoferrite by γ-irradiation

“…Many researches have studied the radiation-induced effects on such materials and facilities with ion beams [18], protons [19], and high-energy neutrons [20] and ␥-ray [21]. Gamma-ray irradiation is known to generate controlled defects of various types such as point, cluster, and columnar defects in the materials [22,23].…”

Development of In-vessel Type Control Rod Drive Mechanism for Marine Reactor

“…With performance tests under the hightemperature and high-pressure water, it can be concluded as follows. 11) These data can lead that the effect of radioactive rays on the material in the present INV-CRDM for MRX is very small. Therefore, it does not need any special measure for irradiation of the materials.…”

LCLS prototype undulator report.

“…Irradiations performed by Cost et al 19 have shown that SmCo magnets had good radiation resistance even at 10 18 n/cm 2 , while NdFeB magnets showed significant degradation at 10 15 n/cm 2 and 10 16 n/cm 2 . However, they also showed that a certain type of NdFeB had significantly higher resistance than the rest though still worse than the SmCo samples.…”