Study For The Influence Of Interfacial Coupling Strength To The Magnetic Properties Of Co/Ni Bilayers

Materials with perpendicular magnetic anisotropy(PMA)have attracted wide atten-tion for its potential application in high-density storage.Magnetic random access memory(MRAM)device is a kind of non-volatile memory device.And because of its advantages of non-volatility,fast access speed,and infinite endurance,it has been considered as the most promising memory device.However,to further increase the storage density,we have to accelerate the application of materials with PMA in MRAM.The object of this thesis,Co/Ni bilayer,is a typical magnetic layer material with large PMA.It is really sig-nificative to study the magnetic properties of Co/Ni bilayers for its application in MRAM.Focus on the Co/Ni bilayer,we studied the influence of interfacial coupling strength to the static magnetic properties and the magnetic dynamics.The specific research content is shown as follows:First,for the static magnetic properties of Co/Ni bilayers,macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by the mi-cromagnetics simulation method.We investigated that when the bilayer systems in the cases of strong coupling,the reversal of Co phase and Ni phase behave as a entirety with each other.And then we discussed the magnetic behavior when the two phases become decoupled as the decreasing of the coupling strength.In addition,the change of coercivity of the bilayers with the increasing of interfacial exchange coupling was studied and the critical behavior in the process was analyzed.The results would apply effective basis for the design and application of MTJ.Meanwhile,for the dynamic magnetic properties,the interfacial effect on laser in-duced ultrafast demagnetization dynamics was investigated by atomistic spin dynamics model.The relationship of microscopic damping constant and ultrafast demagnetization was determined.And then,for magnetization recovery process,we studied the influences of damping constant to the recovery time under various peak electron temperatures.Fur-thermore,as the interfacial exchange coupling increasing,demagnetization curves for Co and Ni was discussed,which is the demonstration for the transition from two-phase phe-nomenon to single-phase phenomenon.This work can open a novel avenue to manipulate the ultrafast demagnetization via interfacial exchange coupling constant in perpendicular magnetic anisotropic Co/Ni bilayers,and it has an immediate implication of the design of high frequency spintronic devices.Finally,the conclusion of the thesis is summarized.