A plasmonic Surface-enhanced Raman Spectroscopy (SERS) sensor has been used for emulation of Near Field Transducer (NFT) in Heat-Assisted Magnetic Recording (HAMR). Laser heating mechanism by the sensor is the same as that by NFT with electro-magnetic near-field or plasmonic field, which is different from far field heating.
Heating behavior for a lubricant film on a carbon overcoat for a hard disk medium was observed using Surface-enhanced Raman Spectroscopy with the plasmonic SERS sensor. Spectral change of lube films in laser heating with a continuous power changer was measured with heating temperature, calculated by anti-Stokes/Stokes intensity ratio in Raman spectra. As a result, it is found that the lubricant film composed of a tetraol perfluoro-polyether (PFPE) is evaporated above 290°C, which shows good agreement with that by TGA (Thermogravimetric Analysis).
The evaporation occurs in wide range of spacing between the lubricant film and the SERS sensor from 0 (contact) to 50nm, and more. After laser heating, lubricant film with free surface in a large gap area, i.e. spacing of 3nm, is recovered with elapsed time. However it is difficult to be recovered in confined (contact) area, because lubricant mobility is small. Lost lubricant can be recovered in head flying by surface diffusion or centrifugal force during disk rotation.