Research On Magnetomechanical Properties Of Magnetic Disk And Its Cotact Demagnetization Behavior Under Thermomechanical Coupling

With the big data era coming,hard disk storage technology,whose magnetic storage density and magnetic recording speed have been developed rapidly,is as an important carrier of information,so the distance between the slider and the disk will continue to reduce.Even in order to achieve more than 1 Tb/in2 ultra high density magnetic storage target,the distance should be reduced to less than 2 nm so as to ensure the high signal resolution requirements of the magnetic read-write head.But in such a small space,once the disk runout,slider random vibration,air pollution,lubricant transfer,etc.occur,it is likely to cause the slider-disk contact,leading to plastic deformation and rapid temperature rise of the disk,eventually the contact interface failure,the immeasurable data loss and other issues appear.In this way,the contact behavior between the slider and the disk has become one of the important reasons for the data loss in the current and future magnetic storage devices.However at present,during the slider-disk contact the magnetic variation and disk demagnetization mechanism is still not clear,so it is difficult to provide some technological supports for avoiding the demagnetization occur due to the slider-disk ccontact.Therefore,the magnetic behavior related with the slider-disk contact is investigated by using the micromagnetic simulation method,finite element method and experimental method,including the following contents:According to the effect of plastic deformation on the magnetic domain,from the aspects of the dislocation pinning and residual stress,magnetic yielding energy formula and the stress energy formula are derived for the by using the domain wall pinning model and inverse magnetostriction principle.And in the magnetic yielding energy formula,the characteristics of the vector,tension-compression,and film thickness change are added.Thus,according to these two energy formula,the magnetic yielding model based on micromagnetic theory can be established.Moreover,the two kinds of solving methods of the magnetic yielding model baesd on the micromagnetic theory are also given.Thus,the construction of the magnetic yielding model is improved.The nanoscratch experiments are applied to simulate the magneto-mechanical behavior associated with the slider-disk contact.And through the phase imaging principle of magnetic force microscopy,a quantitative detection method is proposed.So this paper determines the critical demagnetization condition and the effect of the slider-disk contact force,the disk surface damage degree as well as the slider-disk repeated scrathing times on the magnetic change of the disk.Subsequently,based on the slider-disk sliding contact finite element model and magnetic yielding model,the magnetization evolution of the magnetic disk induced by the magneto-mechanical behavior of the slider-disk contact,which can not be obtained in the nanoscratch experiments is revealed.In addition,comparing the results of the nanoscratch experiments with those of the corresponding simulations in the study of the magneto-mechanical of the magnetic disk,the correctness of the magnetic yielding model built is verified.By combining the random thermal disturbance,Voronoi model characteristics and modified micromagnetic theory,this paper establishes a Voronoi micromagnetic simulation model relating to thermomechanical coupling.Thus,the effect of the magnitude,direction and tension-compression of the plastic strain/elastic stress on the magnetization of the perpendicular magnetic recording medium under the temperature is obtained.Meanwhile,based on the slider-disk high speed sliding finite element model,this paper further reveals the influence of the magnetic moment deflection on the magnetic information decay during the slider-disk contact demagnetization,and gets the effect of the slider-disk contact force,scrathing speed on the medium SNR in relation to trasition noise.And then,the collision experiment between the stainless steel ball and the disk is used to determine the correctness of the slider-disk high speed sliding finite element model and the Voronoi micromagnetic simulation model.Under the slider-disk contact,through altering the thermodynamic properties of the disk medium,the structure dimensions and magnetic material properties of the magnetic disk medium,the interface parameters of the slider-disk contact,this paper obtains that the effects of the antidemagnetization performance of the magnetic disk medium,which can achieve to improve the capacity of high temperature resistance,anti-high stress and strain resistance in the magnetic recording layer or keep the record state good in a magnetic recording layer.In particular,this paper not only considers how to prevent the demagnetization of the disk medium due to the slider-disk contact,but also takes into account the trilemma solution.