Study On Magnetoelectric Properties Of M-Type Hexaferrite And Magnetic Properties Of Films

As a new magnetoelectric coupling material,hexaferrite can induce ferroelectric polarization due to their special magnetic structure,which has a good application prospect in nonvolatile memory technology,four-state logic devices and magnetoelectric sensors.This paper mainly studies the magnetoelectric coupling properties of M-type hexaferrite blocks and the magnetic properties of M-type hexaferrite films.The main research contents and conclusions are as follows:1.Single-phase polycrystalline samples of BaFe₁₂O₁₉ and BaFe_10.2Sc_1.8O₁₉ were prepared by the solid-phase method.The magnetoelectric properties of BaFe_10.2Sc_1.8O₁₉showed that there was magnetoelectric coupling behavior at room temperature.Diffraction of X-rays（XRD）results show that Sc³⁺doping increases the Fe（2）-O-Fe（4）bond angle of BaFe₁₂O₁₉ system from 143.8°to 148.3°.This bond angle is the key to the magnetoelectric coupling performance of BaFe_10.2Sc_1.8O₁₉ system.2.Single-phase polycrystalline samples of BaFe_10.2-xAl_xSc_1.8O₁₉（x=0.2,0.4,0.6,0.8）and Ba_1-xSr_xFe_10.2Sc_1.8O₁₉（x=0.01,0.05,0.07,0.1）were prepared by solid phase method,and their magnetoelectric properties were investigated.The results of XRD and SEM showed that both of them were single-phase polycrystalline samples with uniform grains.（1）The XRD results of Al³⁺doping showed that the bond angle of Fe（2）-O-Fe（4）changes little when x≤0.4,and decreases when x≥0.6.The magnetoelectric coupling coefficientγchanges little when doping amount x≤0.4,which corresponds to the change of bond angle.The dielectric temperature spectra show typical dielectric relaxation behavior,which accords with Arrhenius’law.（2）The XRD results of Sr²⁺doped samples show that Fe（2）-O-Fe（4）bond Angle presents irregular changes,which may be because since the addition of Sr²⁺has little effect on the bond angles and there are errors in finishing.When the doping amount x≤0.07,the magnetoelectric coupling coefficientγdecreases first and then increases.3,Was prepared using pulsed laser deposition method to Sr₃Al₂O₆ as buffer layer Sr Ti O₃/Sr₃Al₂O₆/BaFe₁₂O₁₉ heterojunction thin film,and explores the magnetic changes.Firstly,the influence of annealing time of 10 min,30 min,60 min and 120 min on the magnetic properties of the film was explored.With the increase of annealing time,the coercivity and remanence ratio gradually increased,while the saturation magnetization gradually decreased.The coercivity of the film with an annealing time of 5 min was 8536Oe and the remanence ratio was 0.83.With the increase of Sr₃Al₂O₆ thickness,the saturation magnetization decreases gradually,the coercivity increases gradually,and the remanence ratio increases first and then decreases.When Sr₃Al₂O₆ film is coated for 2 min,the maximum saturation magnetization is 233 emu/cm³.Sr₃Al₂O₆ as a buffer layer significantly increases the coercivity to remanence ratio of M-type films.