*3.2. SEM Image*

High-resolution cross-sectional field emission scanning electron microscope (SEM) images of the as-deposited and annealed 350 ◦C samples are shown in Figure 2a,b. It can be seen from the results of the SEM that the annealed CoFeW film is denser than the as-deposited state. A high-density CoFeW film is obtained by using annealing treatment. The plan views of the as-deposited and annealed 350 ◦C samples are shown in Figure 2c,d. From the SEM results, the as-deposited CoFeW film showed a loose surface morphology.

**Figure 2.** Cross-sectional SEM images of CoFeW 50 nm. (**a**) RT and (**b**) annealed at 350 ◦C. SEM micrographs of CoFeW 50 nm. (**c**) RT and (**d**) annealed at 350 ◦C.
