Investigating The Behaviors Of Phonon And Magnon By Brillouin Light Scattering

Since the frequency of the spin wave is in the microwave frequency range,the spin wave devices based on magnetic nanomaterials and micromachining technology have more and more application prospects.Because the wavelengths of spin waves(magnons)and lattice vibrations(phonons)in the microwave frequency range are both on the order of hundreds of nanometers,this makes the magnon-phonon coupling in the microwave frequency range a way to regulate spin waves or realize information transmission.Brillouin light scattering(BLS)can realize the wave vector resolution test of magnon and phonon without damage by light scattering method,so as to realize the study of magnetic and elastic properties of materials.Therefore,in this article,based on the improvement of the BLS scattering spectrum,we have carried out research on the characteristics of magnons and phonons in materials and their variation with temperature,and studied the phenomenon of magnon-phonon coupling.The main conclusions obtained are as follows:1.In terms of improving the BLS scattering spectrum signal,we propose the methods to improve the resolution and signal-to-noise ratio and to use a flexible buffer layer to improve the signal intensity of the film surface wave.By changing the scan amplitude of the Fabry-Pérot interferometer for multiple scans,the BLS spectrum of the multiple scans is superimposed,and the spectral resolution of the BLS is improved.After superposing four BLS spectra with different scan amplitudes,the peak position fitting error can be reduced by half.Adding a flexible buffer layer improve the surface acoustic wave signal intensity of the film material,and the BLS spectrum intensity of the surface acoustic wave is increased by 4.7 times by adding a flexible polymer buffer layer between the Fe Ni film and the Si substrate.2.We study the temperature-dependent characteristics of magnons in magnetic materials by the changes of BLS peak frequency,half-height width and intensity.Among them,the magnon scattering peak frequency of yttrium iron garnet(YIG)bulk and Fe Ni film decreases with increasing temperature,and the signal intensity increases with increasing temperature.The FWHM of Fe Ni film magnon scattering peak increases with increasing temperature.The changing law of the magnon spectrum is consistent with Curie's law describing the temperature dependence of magnetic materials.3.The temperature-varying phonon properties of the material are studied.The BLS peak frequency of phonons tends to increase with increasing temperature.It is found that the phonon frequency of Si changes more obviously with temperature than that of YIG,which is related to the elastic properties of the material.4.We study the coupling of thermally excited phonons and magnetons by BLS.The magnonphonon coupling phenomenon is studied by changing the external magnetic field and continuously adjusting the magnon frequency of the magnetic material to make the magnon and phonon energy close.At the intersection of the magnon and phonon dispersion curves,the BLS peak of the magnon split at about 0.3 GHz.