Structure and magnetic properties of magnetostrictive compounds Tb_0.36Dy_0.64(Fe_0.85Co_0.15)_2-xB_x (0≤x≤0.15)

Crystal structure and magnetic properties of magnetostrictive compounds Tb_0.36Dy_0.64(Fe_0.85Co_0.15)_2-xB_x (0≤x≤0.15) have been investigated at room temperature. The matrix of these compounds keeps a cubic MgCu₂-type structure. Lattice parameter a of the Laves phase decreases to reach a minimum at x=0.10, then increases with increasing boron content. Through analyzing the Mössbauer spectra, the easy magnetization direction (EMD) for all samples is confirmed to lie along 〈111〉 direction at room temperature, suggesting the presence of the giant magnetostriction. The mean hyperfine field H_hf and the deduced iron moment μ_Fe increase with increasing boron content, resulting in the enhancement of both Curie temperature T_C and spin reorientation temperature T_r. Although the addition of B enlarges the magnetocrystalline anisotropy constant K₁, the composition dependence of the ratio λ/K₁ for Tb_0.36Dy_0.64(Fe_0.85Co_0.15)_2-xB_x, however, reaches a maximum value at x=0. 05 under high magnetic fields.