Acoustic Mode And Optical Mode Resonance Study Of Soft Magnetic Film With Fringe Domain Structure

The magnetization distribution state of the stripe domain structure film is neither completely in-plane nor out-of-plane,which makes the film exhibit novel dynamic magnetic properties including acoustic and optical modes resonance.In general,the acoustic mode has high permeability but low resonance frequency,while the optical mode has high resonance frequency but low permeability.In high-frequency measurement,the optical mode resonance is not obvious and easy to be ignored.Therefore,it is an important development direction in the field of microwave soft magnetic thin films to study the magnetic regulation and mechanism of the thin film with stripe domain,and to prepare stripe domain thin films with high resonance frequency and high permeability at the same time.In this dissertation,the thin film with stripe domain is taken as the research object to study and control the microwave magnetism of the acoustic and optical modes resonance in the film.The main research contents are as follows:The effect of the film thickness on the microwave magnetic properties of the Permalloy film with stripe domain structure.(1)Explore the preparation conditions of Permalloy films with stripe domain.By changing sputtering power,stripe domain films with good acoustic and optical modes resonance were prepared.The results show that the increase of deposition rate caused by high sputtering power makes it easier to form stripe domain structure.(2)Study the effect of thickness on the acoustic and optical modes of the stripe domain.A wedge structure Permalloy film with a thickness ranging from 26 nm to 369 nm was prepared.The results show that a detailed spin transition of the wedge film ranging from the in-plane to out-of-plane regime.The appearance of the stripe domain structure makes the exchange anisotropy of the film increase first and then decrease,so the wedge film shows a higher resonance frequency in the critical thickness region,but the film with the obvious stripe domain structure is unfavorable to improve the acoustic and optical modes resonance frequency of the film.The regulation of acoustic and optical modes resonance in films with stripe domain.(1)Regulation of acoustic and optical modes resonance of stripe domains by perpendicular magnetic anisotropy.The perpendicular magnetic anisotropy in the film is changed by the sputtering pressure.With the increase of perpendicular magnetic anisotropy,the domain structure shows the evolution from the regular stripe domain structure to the labyrinth domain structure.The result of the microwave magnetism shows that the film with large perpendicular magnetic anisotropy will weaken the resonance of the acoustic and optical modes.(2)The adjustment of the composition on the resonance of the acoustic and optical modes of the stripe domain.The FeCoHf films with different Hf contents were prepared by the composition gradient sputtering.The results show that too much doping of Hf elements will weaken the stripe domain structure and disappear.With the increase of Hf,the exchange effect of the thin film is weakened,and the resonant peak frequency of the thin film is reduced continuously.(3)The shape controls the resonance of the acoustic and optical modes of the stripe domain.Permalloy film with stripe domain are processed into a series of different width micro stripe patterns by micro-nano processing technology.Patterned films still exhibits the structure of stripe domain.The resonance frequency of the acoustic mode and the optical mode of the sample decreases with the decrease of the width of the micro-stripes,and the resonance absorption intensity of the resonance peak decreases with the decrease of the area of Permalloy film in the sample.(4)Regulation of acoustic and optical modes resonance of stripe domains by magnetoelectric coupling.A Permalloy film with stripe domain was deposited on the PMNPT substrate by using the magnetoelectric coupling effect.The results show that the stress produced by PMN-PT in the applied electric field will change the magnetic anisotropy of Permalloy film,and then affect the resonance frequency of Permalloy film.