Raman spectroscopy was used to identify a manganese oxide layer established on iridium manganese (IrMn) thin films. A thin manganese oxide layer on the IrMn surface was created by dropping deionized (DI) water for 30 min. Field emission scanning electron microscope and Raman spectroscopy with a 532-nm laser wavelength were used to investigate the DI-water–exposed IrMn surface. The intensity of the Raman laser beam, varied from 0.05 to 50 mW, was carefully optimized to avoid laser-induced heat effects on the manganese oxide layer and IrMn thin film. The results showed that the laser-induced heat produced an α-Mn3O4 phase on the IrMn surface and a manganese oxide layer at 25 mW. Raman optimization was used to investigate the DI-water corrosion and manganese oxide structures on different areas of the IrMn surface.