Influence Of Doping And Patterning On Dynamic Magnetic Properties Of Fe-based Soft Magnetic Thin Films

Ferromagnetic resonance and spin wave resonance are the collective excitation modes of magnetic moments in ferromagnets.Soft magnetic thin films are widely used in electronic devices because of their high resonance frequency and permeability.In recent years,electronic devices have been developing towards miniaturization,high-frequency,integration and multi-frequency,which have raised higher requirements for the application of soft magnetic film.Therefore,it is necessary to study the dynamic magnetic properties of soft magnetic films.This thesis focuses on the dynamic porperties of Fe-based films were prepared by electrochemical deposition and magnetron sputtering methods.In addition,the spin wave excitation of patterned Py alloy thin films was studied.The main contents are as follows:1.The influence of C and Ce element doping on the magnetic properties of FeCo alloy films was studied by electrochemical deposition at different process parameters.It was found that doping concentration could adjust the crystal structure of the sample,and it was also found that doping could optimize the soft magnetic properties of FeCo films.In addition,the parameters of electrodeposition can adjust the coercivity and resonance frequency of the samples.2.The FeNi-MgO particle films were successfully prepared by the co-sputtering method.Dynamic magnetic properties of FeNi-MgO were controlled by the MgO sputtering power,the inclined sputtering angle,and the heat treatment temperature.The results show that the MgO sputtering power can adjust the resonance frequency and damping of the sample,and the inclined sputtering is also an effective method to adjust the resonance frequency.Moreover,after the thin films were heat treated at 200^oC and 500 ^oC annealing,the magnetic spectrum showed two resonance modes.Dynamic magnetic properties of FeNi-MgO films with different thickness were studied.Hysteresis loops show that all samples have the stripe domain structure.The permeability spectra show that all samples have ferromagnetic resonance?FMR?and perpendicular standing spin wave?PSSW?resonance modes.With the thickness increases,?_max?of the PSSW mode unchanged;however,?_max?of the FMR mode decreases.This can be attributing to the damping.The VNA-FMR results show that the critical magnetic field for the PSSW mode to disappear increase as the film thickness.3.The effect of the applied magnetic field angle on the spin resonance of FeNi-MgO particle films was studied by the ESR method.The results show that seven resonance modes can be excited in the thickness direction for the FeNi-MgO thin film with a thickness of 197 nm,and the resonance mode can be adjusted by changing the angle between the external magnetic field and the sample normal.By analyzing the relationship between the resonance field and the mode index n under the DC magnetic field parallel to the film plane,the exchange stiffness constant D/g?_B=15.58 T?nm²was obtained.When the DC magnetic field is vertical to the film plane,we can obtain the surface deformation coefficient of the sample?=0.14 by analyzing the relationship between the resonance field and the mode index n.In addition,the properties of the microstrip antenna with FeNi-MgO and Permalloy magnetic film were studied.The results show that the resonant frequency of the microstrip antenna could be reduced by adding magnetic film.In other words,if the resonant frequency of the microstrip antenna fixed,the size of the microstrip antenna will be reduced by adding magnetic film.Moreover,the performance of the microstrip antenna with FeNi-MgO granular film was better than that with Permalloy film.4.Dynamic magnetic properties of patterned Py soft magnetic films have be studied.Firstly,the antidots-like structure can excite resonances at frequencies of 0.9,2.2,and 3.5 GHz simultaneously,multi-frequency resonance is relized.Secondly,the relationship between the resonance mode and the angle in the rectangular-rectangular and rectangular-disk composite patterned structure was studied by ESR method.The results show that there are three resonance modes in the composite structure,among which the resonance intensity and angle-independent resonances are ferromagnetic resonance of Py films,and the rest are the spin wave resonances introduced by the pattern.Changing the angle of the applied magnetic field can regulate the appearance and annihilation of the spin waves.Thirdly,two resonance modes with a frequency interval of more than 1.5 GHz were simultaneously excited in the material-modulated(Fe₂₀Ni₈₀ and Co₂₀Fe₆₀B₂₀)stripe-patterned structure.At the same time,the stripe width can adjust the coercivity and resonance frequency.