Magnetic pinning strength for the new Sm-TM magnetic materials for use up to 550 °C

A new series of Sm(CowFevCuxZry)z alloys has been developed to produce magnets with high intrinsic coercivity Hci at high temperatures for use up to 550 °C. The maximum use temperature is defined as TM, which is the maximum temperature at which the extrinsic demagnetization curve is a straight line. An important feature of the alloys with high TM is a lower temperature coefficient of Hci, β. These magnets have a higher resistance to demagnetization from increasing thermal agitation which occurs with increasing temperature. A study on magnetic pinning field Hp, which will be explained in the text, vs TM was conducted by measuring the initial magnetization curves of the magnets at 25 and 300 °C. The study shows that as TM increases, Hp increase at high temperatures. At 25 °C, all magnets with TM from 250 to 550 °C have Hp higher than 24 kOe, which is too high to be determined using a hysteresigraph. At 300 °C, the magnet with TM=250 °C has Hp=7.0 kOe, and the magnet with TM=550 °C has Hp=15.1 kOe. Higher pinning field at high temperatures (⩾300 °C) provides a greater resistance to thermal demagnetization, which leads to better performance at high temperatures.