Heat assisted magnetic recording (HAMR) generally refers to the concept of locally heating recording media to reduce the coercivity of the media so that the applied magnetic writing field can more easily direct the magnetization of the media during the temporary magnetic softening of the media caused by the heat source. A tightly confined, high power laser light spot is used to heat a portion of the recording media to substantially reduce the coercivity of the heated portion. Then the heated portion is subjected to a magnetic field that sets the direction of magnetization of the heated portion. In this manner the coercivity of the media at ambient temperature can be much higher than the coercivity during recording, thereby enabling stability of the recorded bits at much higher storage densities and with much smaller bit cells.
In one example of a heat-assisted magnetic recording head, an optical planar waveguide is used to deliver light from a remote source to the air-bearing surface (ABS) of the head where it is used to either heat the media directly (e.g. using a solid immersion mirror type HAMR) or stimulate a near-field transducer (NFT) into resonance for heating of the recording medium. The planar waveguide includes a high-index core layer sandwiched between two low-optical index clad layers.
The clad layers are made from Al2O3 and the core layer from Ta2O5. During operation the ABS environment around the waveguide, NFT, and write pole is exposed to temperatures up to 500° C. and air bearing pressures up to 25 atm. In addition the extreme localized heating is believed to generate superheated water vapor from air humidity and material outgassing.