Enhancement of perpendicular magnetic anisotropy and formation of interface in Nd-Dy-Fe-Co-B thick film with Ta spacer layer

Abstract

The perpendicular magnetic anisotropy of Nd-Fe-B films decreases when the film thickness increases above a critical value, owing to the formation of the in-plane texture. To avoid this dilemma, the influences of Ta spacer layers on the microstructure and magnetic properties of Nd-Dy-Fe-Co-B thick films are systematically investigated by varying the number and thickness of Ta spacer layers. With increasing the number and thickness of Ta spacer layers, a great enhancement of the perpendicular magnetic anisotropy is found, while the coercivity maintains around 2 T. According to the analysis of microstructural results, some interfaces are formed, with the Nd-Fe-B columnar crystal and the Nd element aggregation area being the two sides of the interface. It is found that the Ta spacer layer facilitates the formation of the out-of-plane texture. In addition, the Ta spacer layer has the effect of enhancing the pinning effect leading to a high coercivity. Based on first-order reversal curve analysis, the Ta spacer layer can enhance the dipole interaction and reduce the exchange interaction, which reveals that Nd-Fe-B grains are isolated by the Nd-rich phase. This work can help us to prepare thick Nd-Fe-B-based films with high perpendicular magnetic anisotropy and high coercivity for applications in micromechanical systems.