Research On Magnetic Properties And Application Of FeGaB Thin Films

The coupling device based on the magnetoelectric composite film has the characteristics of miniaturization,high frequency,easy integration and dual magnetoelectric tunability,which provides a new direction for the design of micro-nano devices and has a broad application prospect in electronic communication,military,computer,medical and other fields.The strength of the magnetoelectric effect mainly depends on the performance of the piezoelectric and magnetostrictive materials.As a new magnetostrictive material,FeGaB has great potential for magnetoelectric coupling devices because of its strong ductility,low price and good soft magnetic properties.However,because it is a metal alloy film,it will cause large eddy current effect in high frequency applications.Generally,Al₂O₃ insulating layers are introduced to increase the film resistivity and suppress eddy current loss,so as to ensure that FeGaB thin film devices can operate normally in the high frequency bands.In this thesis,the influence of process parameters on the performance of FeGaB thin films was studied,the eddy current suppression effect and magnetic properties of FeGaB/Al₂O₃multilayer thin films were analyzed.Meanwhile,a magnetoelectric device model based on FeGaB/Al N composite films was established by COMSOL,and a magnetoelectric composite film device was fabricated by MEMS technology to explore the application of FeGaB film in high frequency devices.Firstly,by adjusting the magnetron sputtering process parameters such as the sputtering power of Fe Ga target and Btarget,sputtering gas flow rate and sputtering time,the properties of FeGaB monolayer films were studied.When the sputtering power of Fe Ga target and B target were set to 30W and 46W,respectively,the argon gas flow rate was 22sccm,the sputtering time was 2h,the obtained amorphous FeGaB film was 70.1nm thick,the coercivity was reduced to 0.71Oe,the magnetostriction coefficient was 67ppm.Secondly,the suppression effect of thickness and layer distribution of Al₂O₃ films on eddy current loss in 500nm thick FeGaB film was studied to meet the high frequency application of FeGaB films.The[FeGaB(45nm)/Al₂O₃(5nm)]×10 multilayer films were prepared on different substrates,and the results showed that the soft magnetic properties of both were comparable,and the magnetostriction coefficient was about 63ppm,which was slightly smaller than that of monolayer films.In order to further optimize the soft magnetic properties of the multilayer films,annealing operations were performed.As a result,the minimum coercivity was reduced to 9.12Oe.Finally,a FBAR device based on FeGaB/Al N magnetoelectric thin film was modeled and optimized.The accuracy of the FBAR model was verified,and the frequency response of the magnetoelectric coupling effect of the FBAR device driven by magnetic field was simulated.A FBAR devices based on FeGaB/Al N magnetoelectric composite thin film was fabricated by the optimized photolithography process,and its frequency characteristics were tested.