First Prnciples Calculation Of Magneto-optic Effect In Garnet Structure

Magneto-optic effect plays an important role in the fields of optical information storage,optical communication,laser,etc.Since the last century,its application field has become a hot spot for researchers to explore,and the development of magneto-optic effect theory has also been carried out synchronously.The traditional theory of magneto-optic effect has been established and accepted by most researchers.The magneto-optic effect is expressed as polarized light that is split into left-handed light and right-handed light when propagating in the material after being incident.Synthesized polarized light produces a declination angle with incidence,but the microscopic mechanism is still controversial.The current theory proves that the microscopic Faraday angle is determined by the material's dielectric constant tensor,but the material's dielectric tensor is not diagonal.The transition energy level of a material is related to the transition form,so the band structure of the material can be obtained through the first principle,then the microscopic properties of the material can be obtained,and the microscopic mechanism of the increase of the magneto-optical effect of the garnet material can be explained.In this paper,Lu_xBi_3-x-x Fe₅O₁₂,?x=0,1,2,3?material is used as an example to explain the magneto-optic effect in garnet by first-principles calculation and RF magnetron sputtering experimental.First,the Material Stadio software was used to construct the Lu_xBi_3-x-x Fe₅O₁₂,?x=0,1,2,3?material crystal structure and optimize the structure to obtain the best parameter for calculation.The band structure and state density of the film were calculated through this parameter,and found The energy level related to the crystal field effect in the garnet structure and due to the doping of the Bi³⁺ion,the orbital energy level of the Bi³⁺ion appears to be split under the influence of the crystal field effect in the garnet structure,and after the energy level is split The energy level spacing between the orbits of the formed state density is increased and?including the valence band and the valence band to the conduction band?corresponds to the photon transition energy,so the probability of the photon transition is increased,which in turn increases the Faraday angle of the material.Through simulation,it is found that the crystal field effect of the garnet structure is doped with Lu³⁺ions.Lu³⁺ions act as a medium for indirect exchange in the crystal field effect,increasing the crystal field effect of the material.Then we prepared the Lu_x Bi_3-x-x Fe₅O₁₂,?x=0,1,2,3?film on the GGG substrate by magnetron sputtering experiment.The test found that the film's Faraday rotation angle increased linearly with the increase of Bi³⁺ion.From this we know that the reason why the material increases more than Faraday rotation angle at 550nm after Bi³⁺ion doping is that the p-orbit of Bi³⁺ion has an energy level corresponding to the photon transition energy at 550nm wavelength at the top of the valence band.The reason for the increase of the Faraday rotation angle of the film with increased content is the transition in the p-orbital band of Bi³⁺ions.As the content of Bi³⁺ions increases,the energy level splitting phenomenon within the p-orbit occurs.