Behavior of some heavy and light rare earth-cobalt magnets at high temperature

This article reports our investigation on the behavior of some heavy and light rare earth-cobalt magnets at high temperatures. Magnetic properties and the temperature coefficients of magnetization, α, over a wide temperature range have been studied for various magnets, which include RE(Co0.74Fe0.14Cu0.09Zr0.03)7.4 for RE=Er, Dy, Tm, Ho, and Tb, as well as RE(Co0.68Fe0.22Cu0.07Zr0.03)7.4 for RE=Sm, Ho, and Gd. The results show that the temperature for magnetization peak is 480 °C for the Er–Co magnet, and 370 °C for the Ho–Co magnet. Our research indicates that there is good potential for making temperature compensated, high temperature magnets with Ho, Er, Gd, or combinations of these rare earths to satisfy certain applications. The Tm–Co magnet does not show the typical characteristic shown by other heavy rare earth cobalt magnets, which is a positive α at points above room temperature. However, Tm–Co shows a small and near constant negative α value, which may be useful for some applications. Magnetic properties and the temperature dependence for temperature compensated magnets with high coercivity are also reported in this article, which have the composition of Sm0.6RE0.4(Co,Fe,Cu,Zr)7.4 with RE=Er, Ho, Tm, Dy, and Tb.