Influence of Cu-content on the hard magnetic properties of Sm(Co,Cu) 2:17 compounds

Sm(Co1-xCux)7.8alloys with 0.07<x<0.20 were investigated magnetically and metallographically with single crystal. These alloys are at elevated temperatures within the 2:17 homogeneity region. They show magnetic hardness in bulk form, caused by pinning of the domain walls at precipitates of the Sm(Co, Cu)5type. Annealing at about 1070 K yielded maximum coercive fields,IHc. The dependence of the coercivity maximum on the Cu-content shows no correlation with the primary magnetic properties of both matrix and precipitate phase. Domain wall energies were determined by means of the magneto-optical Kerr-effect. Coercive fields in bulk samples are obtained when the domain wall energy within the precipitate phase is lower than within the matrix, i.e. there is an attractive interaction between domain wall and precipitates.