Temperature dependence of coercive force and nucleating fields in Co5Sm

In Co5Sm, the coercive force of aggregates of powders or sintered magnets is much greater at 77 K than at room temperature. In single particles, the field at which an individual magnetization jump occurs increases rapidly and monotonically with decreasing T. On the other hand, the K reported for Co5Sm is the same at 77 K and room T, with a broad maximum between. It thus appears that the reversal process is not controlled by the properties of bulk Co5Sm. The observed T dependence must be ascribable to the imperfections that govern the magnetization reversal process.