Structure and magnetic properties of mechanically alloyed SmZr(Co,Fe) nanophase hard magnets

In this paper, Sm_zZr_y(Co_1-xFe_x)_100-x-y (nominal composition) powders, where 13 ≤ z ≤ 15, 0 ≤ y ≤ 5, and 0 ≤ zx ≤ 0.5, were prepared by mechanical alloying, and annealed using an optimized procedure. As-milled powders were amorphous, or showed some small α-Fe crystallites, depending on Fe composition. Initially, powders with y = 0 were prepared with a view to optimize the Fe content, and it was found that x = 0.1 was the best Fe content for all Sm compositions. Samples without Zr showed a mixture of Th₂Ni₁₇ and Th₂Zn₁₇ structure types, as well as SmCo₅, and μ₀H_c was high as 1.6 T. Powders were then made varying x and y, and keeping z = 0.1. These samples also showed a mixture of Sm₂Co₁₇ phases along with SmCo₅, dependent on Zr content. Room-temperature coercivities greater than 2.0 T were observed. Enhanced remanence (σ_r/σ_s ≥ 0.65) is achieved in all compositions, indicating intergrain exchange coupling among the fine grains.