Physical Properties of Rare Earth-Cobalt Magnet Materials

The magnetization of a number of commercial SmCo5 magnets has been measured as a function of stress and temperature. These measurements are significant to present and proposed applications of the magnets and also to characterization and an understanding of the mechanisms involved. Application of a compressive stress of 10,000 psi, which is near the strength of the material, has a negligible effect at temperatures up to 215 C, at least. Heating the sample, on the other hand, induces not only the previously studied reversible and irreversible losses, but also time-dependent and permanent loss. The time- dependent losses indicate a range of relaxation times. The dependence of these relaxation times and of the permanent loss on external parameters and on sample history is complicated, and only preliminary characterization has been obtained to date, as illustrated by a number of examples.