Effects of Hf addition on the microstructure, magnetic properties and coercivity mechanism of Nd-Ce-Fe-B ribbons fabricated by melt-spinning technique

In this paper Hf doped (Nd_0.8Ce_0.2)₁₃Fe_82−xB₅Hf_x (x = 0, 0.5, 1.0, 2.0, 3.0) ribbons were fabricated by melt-spinning technique, and their microstructure, magnetic properties and coercivity mechanism have been investigated methodically. It is found that the coercivity of (Nd_0.8Ce_0.2)₁₃Fe_82−xB₅Hf_x ribbons is enhanced for 0 ≤ x ≤ 2.0 at.% while the remanence decreases slightly. The optimal comprehensive magnetic properties J_r = 7.5 kG, H_cj = 12.7 kOe, and (BH)_max = 12.3 MGOe, are obtained at x = 1.0 at.%. The grain size decreased with the addition of Hf and more uniform microstructure evolved. The coercivity mechanism of the (Nd_0.8Ce_0.2)₁₃Fe_82−xB₅Hf_x (x = 0–3.0) ribbons is found to be the pinning mechanism based on the systematic investigations and analysis. The synchronization of the grain refinement and the pinning effect lead to the improvement of magnetic properties.