Achievement of High Perpendicular Anisotropy and Modification of Heat Treatment Peeling in Micron-Thickness Nd-Fe-B Films Used for Magnetic MEMS.

ABSTRACT

Thick Nd-Fe-B permanent magnetic films with good perpendicular anisotropy have important applications in magnetic microelectromechanical systems (MEMSs). However, when the thickness of the Nd-Fe-B film reaches the micron level, the magnetic anisotropy and texture of NdFeB film will become worse, and it is also prone to peeling during heat treatment, which seriously limits their applications. In this paper, Si(100)/Ta(100 nm)/NdxFe91-xB9(x = 14.5, 16.4, 18.2)/Ta (100 nm) films with thicknesses of 2-10 µm are prepared by magnetron sputtering. It is found that gradient annealing (GN) could help improve the magnetic anisotropy and texture of the micron-thickness film. When the Nd-Fe-B film thickness increases from 2 µm to 9 µm, its magnetic anisotropy and texture do not deteriorate. For the 9 µm Nd-Fe-B film, a high coercivity of 20.26 kOe and high magnetic anisotropy (remanence ratio Mr/Ms = 0.91) are achieved. An in-depth analysis of the elemental composition of the film along the thickness direction is conducted, and the presence of Nd aggregation layers at the interface between the Nd-Fe-B and the Ta layers is confirmed. The influence of thicknesses of the Ta buffer layer on the peeling of Nd-Fe-B micron-thickness films after high-temperature annealing is investigated, and it is found that increasing the thickness of the Ta buffer layer could effectively inhibit the peeling of Nd-Fe-B films. Our finding provides an effective way to modify the heat treatment peeling of Nd-Fe-B films. Our results are important for the development of Nd-Fe-B micron-scale films with high perpendicular anisotropy for applications in magnetic MEMS.