Interpretation of the magnetic properties of pseudobinarySm2(Co,M)17compounds. I. Magnetocrystalline anisotropy

The magnetocrystalline anisotropy of ${\mathrm{Sm}}_2{(\mathrm{Co},M)}_{17}$ and ${\mathrm{Y}}_2{(\mathrm{Co},M)}_{17}$ compounds, with $M=\mathrm{F}\mathrm{e},\mathrm{M}\mathrm{n},\mathrm{o}\mathrm{r}\mathrm{C}\mathrm{r}$, has been measured as a function of composition and temperature. The data yield the itinerant-electron and crystal-field contributions to the anisotropy. From the former, the role of band-structure changes is judged to be of equal importance to preferential substitution effects in determining the type and magnitude of the transition-metal sublattice anisotropy. A simplified single-ion crystal-field theory is used to derive the exchange- and crystal-field parameters. The magnitude of their variations cannot be explained by magnetic-moment and lattice-parameter changes alone. Calculations for the structure concerned suggests that in the crystal-field case, charge-transfer effects may be important. However, both changes in the atomic coordinates and in the conduction-electron concentration can also be relevant to both crystal-field and exchange-field concentration dependences.