The microstructure and magnetization reversal behavior of melt-spun (Nd1-xCex)-Fe-B ribbons☆

In this study, the alloy ingots with nominal compositions of (Nd1−xCex)31FebalCo0.2Ga0.1B (x = 0, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%) were prepared and then melt-spun to form nanocrystalline ribbons at the wheel speed of 20 m/s. XRD results show that all melt-spun ribbons exhibit the tetragonal structure (Nd,Ce)2Fe14B phase with the space group P42/mmm. The Curie temperature and lattice constant decrease with the increase of Ce content. The Curie temperature decreases gradually from 306 to 247 °C with the increase of Ce content. Those results indicate that Ce element has been incorporated into Nd2Fe14B main crystalline phase and formed (Ce,Nd)-Fe-B hard magnetic phase. It is also found that the remanence ratio (Mr/Ms) decreases from 0.693 to 0.663 and the coercivity (Hc) decreases from 18.7 to 14.2 kOe with the increase of Ce content. However, a relatively high coercivity of 18.3 kOe for (Nd1−xCex)31FebalCo0.2Ga0.1B (x = 0.2) melt-spun ribbon is achieved. The coercivity is sensitive to microstructure. The AFM patterns show the sample (x = 0.2) has the most uniform and finest microstructure. The magnetization reversal behavior (δM plots) is discussed in detail. The positive δM value is observed in every sample, which confirms the existence of exchange coupling interaction. Evidently, the δM maximum value reaches 0.9 in the sample (x = 0.2). It is indicated that the intergranular exchange coupling effect is the strongest, which is consistent with coercivity enhancing.