Large anisotropy fields in hexagonal R 2- xT 17+2 x

A series of alloys with the hexagonal Th ₂Ni ₁₇-structure (Pr _0.8Sm _0.6M _0.8)(Fe _{17- y}Co _y) where M = (Zr+Fe) or (Ti+Fe), have Curie temperatures ⩾ 700 K when y ⩾ 5. The excess iron is located on the 4e dumbell site. The average iron hyperfine field is about 31.5 T. All alloys have an easy c-axis with a room temperature anisotropy field in the range 3-4 T. The sign of A₂₀ is opposite for the 2b and 2d rare-earth sites: A₂₀(2b) = (-170±20) K a^-2₀ and A₂₀(2d) = (+100±20) K a^-2₀, and the anisotropy is attributed to some appropriate preferential occuption of the two sites by rare-earths with opposite sign of the second-order Stevens coefficient α _J.