Formation of δ phase and its effects on magnetic properties and magnetostriction of Tb0.5Pr0.5(Fe0.4+xCo0.6−x)1.9 (0⩽x⩽0.6)

Structure, magnetic properties and magnetostriction of Tb0.5Pr0.5(Fe0.4+xCo0.6−x)1.9 (0⩽x⩽0.6) alloys are investigated. The existence of the δ phase for 50% Tb and 50% Pr is beneficial to the formation of the MgCu2-type Laves phase. The composition dependence of Curie temperature has the same trend as the Slater–Pauling curve for the moment of Fe–Co alloys. The saturation magnetization Ms and the remanence MR decrease, whereas the coercivity iHc increases with decreasing Co content, due to the increased amount of the non-cubic PuNi3-type phase. The polycrystalline magnetostriction |λ∥−λ| of the alloys at room temperature increases with increasing magnetic field and does not achieve saturation up to 796kA/m.