Evolution and effects of surface degradation layer of Sm2Co17 magnets at high temperatures

The long-term application of SmCo-based magnets at high temperatures has been restricted by the irreversible loss of magnetic properties. In this work, degradation behavior of Sm2Co17 magnets was studied at 500 degrees C in air and vacuum by being focused on the surface degradation layer. The structure and the composition of the degradation layer were studied experimentally, and the magnetization was calculated to certify the deduction of the irreversible loss. The soft magnetic phases in the degradation layer can result in the decline of the magnetization and the irreversible loss of magnetic properties. Furthermore, the controversial formation reason of the degradation layer was also studied. It was found that the diffusion of the oxygen, but not the sublimation of Sm, could be the dominant formation reason of the degradation layers. (C) 2014 AIP Publishing LLC.