From the locally enlarged image, it can be seen that the diffraction peak corresponding to Fe3O4 gradually increases from NPD1 to NPD6 surface, which means that the Fe3O4 film gradually thickens.
From the local enlarged image, it can be seen that the diffraction peak corresponding to Fe3O4 gradually increases from NPD1 to NPD6 surface, which means that the Fe3O4 film gradually becomes thicker.