Research On The Migration And Dissipation Mechanism Of The Head Disk Lubricant In The Helium-filled Heat-assisted Magnetic Storage Hard Dis

In the early 2020 s,the development of technology has entered the era of intelligent technology.This also poses new challenges to the technical requirements of data storage.Hard disk drives(HDDS)are widely used due to the storage stability and low price.To improve the storage capacity of HDDs,Thermal Flying-height(TFC)and Heat Assisted Magnetic Recording(HAMR)were proposed.The proposed TFC reduced the spacing of the head-disk to a few nanometers.Under such a spacing,the lubricant film attached to the surface of the disk will become unstable,causing the lubricant transfer to the head,which will pollute the head and fail its performance.Therefore,it is very important to explore the mechanism of lubricant transfer in the space of the head-disk interface.At the same time,when the head is heated by thermal resistance,a thermal bulge is formed to reduce the flight height of the head.Moreover,the heat generated by thermal resistance requires that the head and the interface space between the head and disk have good heat dissipation performance.Therefore,improving the heat dissipation of the interface space of the head and disk is conducive to improving the service performance of the hard disk.In addition,pulse laser heating of magnetic medium in the HAMR will also cause the temperature rise of lubricant on the disk surface,thus causing the evaporation and dissipation of lubricant.Hence,it is helpful for the design of the HAMR magnetic head to understand the transfer behavior of lubricant at the head-disk interface under Thermally Assisted Magnetic Recording.Based on this,the following research is carried out in this paper and corresponding conclusions are drawn.(1)A head-disk interface air-floating bearing model was established,and the air in the head-disk interface was replaced with helium or helium-air mixed gas.The influence rules of pressure difference,temperature difference and heat flux difference between the head-disk interface were investigated by helium fraction,lubricant thickness,environmental pressure and flight altitude.Then,the heat dissipation rules of hard disk induced by different helium fraction,lubricant thickness,environmental pressure and flight altitude were revealed.The results show that the presence of helium increases the heat dissipation of the head-disk interface,and the increase of lubricant thickness and environmental pressure is more beneficial to the heat dissipation of the head-disk interface than the flight altitude.(2)In order to investigate the effect of helium fraction on lubricant transfer,a molecular dynamics coarse-grained model of lubricant transfer in the head-disk interface under helium-air mixed gas was established in this paper.The pressure differences at the head-disk interface under different helium fractions obtained by air bearing were input into the model.From a microscopic perspective,the effects of helium fraction,environmental pressure,lubricant thickness,disk speed and initial pressure on lubricant transfer volume were analyzed.The results show that the transfer amount of lubricant decreases with the increase of helium fraction,and the inhibition of helium fraction on the transfer amount of lubricant becomes more obvious when the helium fraction reaches0.6.Meanwhile,under different helium fractions,the transfer amount of lubricant increases with the increase of flight altitude,environmental pressure,lubricant thickness,disk speed and initial pressure.The environmental pressure has the greatest influence on the transfer amount of lubricant,while the initial pressure has the least influence.(3)In order to explore the transfer law of lubricant under HAMR,a molecular dynamics coarse-grained model of lubricant transfer in the head-disk interface space under Thermally Assisted Magnetic Recording was established in this paper.The heat flux at the head-disk interface under different helium fractions obtained by air-floating bearings was input into the model.The effects of pulse heat flux,pulse spot size,disk speed,lubricant type and pulse laser type on lubricant transfer amount,dissipation content,depletion width and depletion depth were analyzed.And the influence mechanism of pulse heat flux on lubricant transfer amount,dissipation content,depletion width and depletion depth was revealed.The results show that the lubricant transfer amount,depletion content,depletion width and depth increase with the increase of laser heat flux.Under different heat flux densities,lubricant transfer amount and depletion content increase with the increase of disk speed,but the width and depth of lubricant depletion are less obvious with the increase of disk speed.What’s more,Zdol4000 lubricant causes the largest amount of lubricant transfer,depletion content,and depletion width and depth of the most serious.However,the influence of continuous heat flux on lubricant transfer amount,depletion content,depth and width is the most intense.Under the action of different laser heat flux,the amount of lubricant transfer shows different trend with the increase of pulse spot radius.