Recovering magnetic domains of nanoscale-mechanically damaged ferromagnetic thin film of information data storage

Abstract

Combined effects of stress and temperature on magnetic domains and scratch morphology of the ferromagnetic film of a perpendicular magnetic recording media are investigated using nanoscratch, atomic force microscope, and magnetic force microscope. The stored magnetic signals in the non-scratched area become weak with increasing temperature due to the thermal agitation of magnetic spins. The high local stress permanently damages the magnetic signals at the scratch center. However, the weakened magnetic signals at lightly stressed regimes recover significantly with increasing temperature up to 300 °C due to the partial recovery of ferromagnetism. Regarding the nanoscratch morphology, when the temperature increases up to 300 °C, the scratch is healed noticeably due to metal oxides (CoO, Cr2O3, and PtO2) built-up on the scratched surface. Surprisingly, the scratch deepens at 400 - 600 °C. This is attributed to PtO2 evaporation and the phase transition of magnetic grains from HCP to FCC.