Strain And Electric Field Regulation Of Ferromagnetic M-type Hexagonal Ferrite Films With Conical Magnetic Structure

The rapid development of artificial intelligence and Internet of things(IOT)technology puts forward higher requirements for the performance of hardware equipment.Miniaturization,integration,flexibility and low power consumption are the development trend of electronic components.In the field of microwave and RF,the tunability of ferromagnetic resonance(FMR)is of great significance for the practical application of microwave devices.The traditional tuning method generally adopts the current coil,which controls the strength of the magnetic field by changing the number of turns and current of the coil.Or directly use the permanent magnet to adjust the strength of the magnetic field by changing the size of the permanent magnet.These two traditional methods can effectively tune the ferromagnetic resonance of materials,and are widely used in various microwave devices.However,the current coil and permanent magnet are not in line with the development trend of miniaturization,flexibility and low power consumption of electronic components because of their volume,which limits the further development of microwave devices.Therefore,it is necessary to find other ways to replace current coil and permanent magnet.In view of the above problems,this paper selects the conical magnetic structure M-type hexagonal ferrite BaFe10.2Sc1.8O19(BFSO)with room temperature magnetoelectric coupling effect as the research object,systematically studies the influence of pure mechanical external force and electric field on the ferromagnetic resonance of BFSO epitaxial films,and analyzes its regulation mechanism combined with the theoretical model.Finally,we further studied the effect of temperature on the FMR properties of BFSO films.The specific findings are as follows:Firstly,in the strain regulation experiment of microwave characteristics of BFSO films,we grew flexible BFSO epitaxial films on mica substrate,and studied the changes of equivalent magnetic anisotropy and FMR properties of flexible BFSO films under different bending radius.The results show that both geometry and bending strain will affect the FMR properties of BFSO films.The magnetic properties of BFSO films can be well regulated by controlling the bending radius.In addition,the FMR spectrum of BFSO film has good bending stability in 1000 bending cycles.Further theoretical analysis shows that the changes of anisotropic field Hk and resonant field Hr in the plane of BFSO film are mainly affected by magnetostriction effect.The resonant linewidth of BFSO thin films ΔH is affected by many factors,and its intrinsic loss(ΔHGilb and ΔHinhom)follows the variation trend of Hr and is based on the external loss of two magnon scattering ΔHTMS is mainly determined by the film geometry.The above results are helpful to better understand and use the flexible BFSO film,so that it can be applied to the future X-band flexible microwave devices.Secondly,BFSO epitaxial films were grown on ferroelectric substrate PMN-PT(111),and the electric field regulation of room temperature FMR characteristics of BFSO films was studied.It is found that when the electric field is applied,when the magnetic field is in the plane,the resonant field can be continuously adjustable up and down of 26 Oe.However,the stress and strain generated by the piezoelectric effect of PMN-PT(111)is along the z-axis direction,and the electric dipole inside the substrate is more inclined to the z-axis direction.Therefore,on the one hand,there will be no large interfacial strain;On the other hand,after the electric field is applied along the z-axis direction,the deflection angle of the electric dipole in the substrate is small,so the coupling effect with the magnetic dipole in the BFSO film is small.In view of the above reasons,the magnetic regulation of the film by electric field is not obvious.Therefore,we tried to grow BFSO films on PMN-PT(100),but due to the large lattice mismatch between them,BFSO polycrystalline films were grown on PMN-PT(100).Finally,we studied the effect of temperature on the FMR properties of BFSO films.It is found that there are two mechanisms for the change of Gilbert damping coefficient a in BFSO films:one is the lattice relaxation caused by rare earth element Sc,which shows that a changes nonlinearly with temperature near room temperature;The other is the linewidth caused by two magnon scattering and magnon phonon scattering,which shows the linear change of a with temperature at low temperature.In addition,in the study of the dependence of the resonance field on temperature,we found that the effective magnetic moment and the spin magnetic ratio are easily affected by temperature,and the change trend of the resonance field is mainly dominated by the change of the spin magnetic ratio.The above research results have important reference significance for understanding the multi field regulation mechanism of FMR performance of BFSO thin film with conical magnetic structure and its application in flexible and low-power devices.