Brillouin Light Scattering Study Of Interface Modulated Dzyaloshinskii-Moriya Interaction

As a special topological magnetic structure,Skyrmion is expected to become the carrier of the next generation of spin electronics devices due to its unique advantages such as rewritability of spin polarized current and transmission at ultra-low current density.The fundamental physical mechanism in generating Skyrmion is Dzyaloshinskii Moriya interaction(DMI).Different from Heisenberg exchange,DMI makes the adjacent spins tend to be tilted with chiral selection,thus forming the topological magnetic structure such as the Skyrmion.Therefore,finding an effective research method to achieve DMI modulation has become an urgent problem to be solved.We use the effect of interfacial DMI on the intrinsic frequency of the interfacial wave vector selected magnetostatic surface spin wave(MSSW)to realize the quantitative measurement of DMI by characterizing the dispersion relation of MSSW in the magnetic film by Brillouin light scattering(BLS).The results show that for Pt/Co films,both the substrate and non-5d heavy metal buffer layer can modulate the interfacial DMI.The main innovative achievements are as follows:1.In FeNi films without a 5d heavy metal interface,the influence of different substrates on the MSSW eigenfrequency of FeNi films and the dependence of Stokes/anti-Stokes(S/AS)peak intensity ratio on the external magnetic field,spin-wave vector and dielectric constant of the substrate were studied by BLS.It is found that the S/AS intensity ratio increases with decreasing in-plane magnetic fields and increasing wave vectors.At the same time,the intensity ratio has a positive correlation with the dielectric constant of the substrate.Finally,no obvious intrinsic frequency shift under the opposite wave vector was found,which indicates that there is no interfacial DMI in this system.2.By growing Pt/Co films of the same thickness on different non-heavy metal substrates to regulate the Pt/Co interface,the regulation of DMI strength has been achieved.In the Pt/Co thin film,the spin-orbit coupling between the 5d electrons in the Pt layer and the 3d electrons in the Co layer would introduce DMI.In this system,we changed the Co/Sub interface by using different substrates(Sub),and studied the dispersion relationship of MSSW intrinsic frequency with wave vector in this system using BLS,and found that the change of the substrate can lead to the change of the interfacial DMI in the system.By analyzing the dispersion relations of the Stokes and anti-Stokes peaks separately,it is found that the change of DMI still comes from the spin-orbit coupling of the Pt/Co interface instead of the substrate interface.3.A non-heavy metal Cu buffer layer with different thickness t was introduced between the Co/Si interface of the Pt/Co/Si thin film.It was found that the intensity of DMI increased with the thickness of Cu from 2 nm to 8 nm,and D increases from306.9?J/m~2 to 620.7?J/m~2.Further analysis shows that the change in DMI still originates from the spin-orbit coupling of the Pt/Co interface modulated by the Cu buffer layer,rather than the Co/Cu interface.This thesis provides a method for the regulation of DMI by the non-heavy metal interface,and the research results may have some reference value for the interface DMI regulation of Skyrmion.