Research On YIG Magnetodielectric Effect And Ferromagnetic Resonance Measurement

Based on previous studies,this paper explores a method that can study the magnetoelectric effect at room temperature and low field conditions.First,high-quality YIG is prepared by metal organic decomposition method,and then mixed with 30wt%paraffin to make a standard ring sample,and the electromagnetic characteristics of the sample in the microwave band of 0.5-10 GHz are measured.By increasing the static magnetic field in the vertical and horizontal directions with respect to the direction of propagation of the microwaves,respectively,the change in the electromagnetic characteristics of the sample with the increase of the bias magnetic field was measured.The experimental results show that the ferromagnetic resonance peak of the sample appears and the dielectric constant shifts.Through the data analysis,the magnetic dielectric effect coefficient of the sample can be calculated,from which it can be clearly seen that the amplitude of the magnetic permittivity of the sample will increase with the increase of the applied magnetic field,and will reach the best value at the ferromagnetic resonance frequency.Compared with the vertical magnetic field method,the experiment under the horizontal magnetic field can observe more obvious phenomena.Discussion and analysis of the experimental results:Since the purity of the prepared YIG is high and there is no Fe2+ in the sample,the influence of the Fe2+-Fe3+dipole on the magnetic dielectric effect can be excluded.Qualitatively speculated that when ferromagnetic resonance occurs,the precession of the magnetic moment around the atom will generate a vortex magnetic field.According to the law of electromagnetic induction,this vortex magnetic field will produce a time-varying electric field,and the induced electric field will change the polarization properties of the central atom,thereby affecting the dielectric constant.When ferromagnetic resonance occurs,the precession amplitude is maximum,and therefore the magnetic permittivity is measured at the maximum value at the ferromagnetic resonance frequency.Ferromagnetic resonance is an important feature of ferromagnetic materials.It can not only be used to study the magnetic permittivity of materials,but also has basic physical significance for the study of spintronics related materials and devices.The second part of this thesis is the study of the short-circuit microstrip ferromagnetic resonance measurement system.The system includes short-circuit microstrip fixtures,gaussmeters,solenoids,vector network analyzers,current sources,and programmable computers.The program-controlled computer-controlled vector network analyzer provides a single-frequency signal source for the short-circuit microstrip line,and controls the current source to output a stable current to the solenoid,so that a uniform and stable magnetic field is generated in the middle region of the solenoid.Change the horizontal magnetic field of the sample,program-controlled computer reads the reflected microwave signal S11,and makes the relationship between the S parameter and the magnetic field curve,through the data processing of the curve diagram to obtain the magnetic resonance film width,gyromagnetic resonance and Lande g-factor.This measurement system uses Lab VIEW programming and development to achieve good data acquisition,data processing,human-computer interaction,and is a powerful tool for studying the ferromagnetic resonance phenomenon of magnetic materials.