Nano-scale air bearing is used for the head disk interface (HDI) and thin lubricant film is covered on the disk to reduce the wear between head and disk. To increase aerial recording density, the head flying height needs to be decreased. Consequently, the probability which contact recording occurs becomes higher. Lubricant thickness is very important for the stability of the HDI system because thicker lubricant film may cause vibration of the head. Generally, it is well-known that surface morphology of the lubricant film affects the performance of read and write of the head. Especially, lubricant depletion due to disk rotation and fluctuation behavior by the head-lubricant interaction have been important topics to investigate for the HDI performance. As of the head-lubricant interaction phenomena, there are many research results. Recently, the heat assisted magnetic recording (HAMR) technology has been being developed to achieve much higher aerial density for the HDD. The HAMR system utilizes the phenomenon of material property variation in magnetic media on the application of heat. Heating by a laser on the disk weakens the magnetic coercivity of the magnetic media, and thus enhances the aerial density dramatically. In HAMR system, a nanoscale heat transfer phenomena is initiated by laser heating, and the energy transport affects physical properties of the media as well as the stability of the system. Therefore, it is necessary to thoroughly understand the heat conduction in sub-continuum regime for the reliability of the recording system. In addition to the conduction inside the media, it is very important to investigate the thermal effect to the lubricant layer.
Femtosecond laser heating technologies have made technical innovation in the related areas and have brought considerable attention to the heat transfer phenomena in the thin metal films. Electrons as well as phonons play a vital role in the energy transport in metals. Thus the thermal behavior of energy carriers, more specifically, electrons and phonons should be considered during theoretical analysis models of predicting the transient sub-continuum thermal transport in metals. Due to the energy transport mechanism with different non-equilibrium temperature characteristics of energy carriers, two-temperature models are widely used.
On the other hand, lattice Boltzmann method (LBM) can be applied to analyze heat transfer. In our previous works, LBM was developed and successfully applied to simulate the heat conduction of phonons. The idea led us to develop a new LBM model to solve the energy transport of electrons and phonons in metals. We demonstrated thin gold film heating via ultrashort laser pulse and studied the electron-phonon coupling methodology.
The heat from laser heating is convected to the air through the lubricant layer. The thermal effects is investigated by using multiphase LBM model considering thermal variation. There are several types of thermal multiphase LBM model. Among them, a model by He et al. will be utilized.
In this multiscale simulation, we can obtain the deeper understanding of heat conduction in metals and convection in multiphase fluids in the HDI system