Mechanisms of flux decay in SmCo5magnets

Until now there has been no adequate explanation of the unusually high flux decay rates found in SmCo5magnets, which are uncharacteristic of a magnet with such outstanding resistance to demagnetization. A comprehensive study of the flux decay phenomenon in SmCo5magnets has been performed using a high resolution, high stability measurement apparatus developed at the Draper Laboratory. The observed instability of the SmCo5magnet has been related to the presence and/or formation of the phases Sm2Co7and Sm2Co17. These results indicate that maximum stability in these magnets can be achieved when the magnet material is composed of stoichiometric SmCo5(with a low oxygen content that remains in solution in the SmCo5lattice at the operating temperature).