Interface change of Pr-Fe-B thin films with different ferromagnetic compositions

Abstract

The thin film structure of the Si3N4/Pr-Fe-B/Si3N4/glass substrate was fabricated by the sputtering process followed by an in-situ annealing process at 650 °C. The changes at the interface of magnetic layer/underlayer were investigated with simultaneous addition of Fe content in the range of 68.9 to 76.61 at.% during the sputtering process. With ferromagnetic properties and more reactive and movable capacity of Fe, the addition of Fe created significant changes in the crystal structure, surface morphology, microstructure, and magnetic properties in Pr-Fe-B thin films. X-ray diffraction results confirmed the presence of two Pr2Fe14B and Pr2Fe23B3 magnetic phases in the thin films. The surface morphology of the thin films observed through SEM pictures and AFM images showed the blossom phenomenon with various grain sizes and surface roughness, respectively. The microstructure of the thin films through HR-TEM pictures revealed the discernable change at the interface of the Pr-Fe-B layer/Si3N4 underlayer. The new Fe3Si underlayer formed different thicknesses at the interface corresponding to various Fe contents. The stacking of (100) and (010) planes of Pr2Fe14B phase with different d-spacings was observed at higher magnification of HR-TEM. Results of magnetic measurement showed that the thin film at 73.32 at.% Fe content had the better growth potential of perpendicular magnetic anisotropy (PMA) and obtained a higher coercivity of approximately 4.5 kOe. MFM images through magnetic domain observation showed that the thin films had the same magnetic domain pattern but varied in magnetic domain size. Analysis of saturation magnetization and effective uniaxial anisotropy of the thin films showed the contribution of the interface magnetic anisotropy (to the PMA with the value of Ki = 122.25 × 106 erg/m2.