Study Of Micromechanism Of Magnetic Field-induced Magnetic Anisotropy In Amorphous CoFeB And Polycrystalline Co Thin Films

Magnetic anisotropy（MA）is an important property of magnetic materials,which not only determines the orientation of magnetic moment in magnetic material,but also influences the working frequency of magnetoelectric devices.Hence,researchers are trying their best to understand the origin of magnetic field-induced magnetic anisotropy perfectly.However,both amorphous CoFeB film and polycrystalline Co film aren’t clear explanation about the question,even if we consider the directional order model.Hence,the main work is as follows:1.We reported a quite significant magnetic field-induced uniaxial MA in amorphous CoFeB thin films containing double ferromagnetic atoms,which can be prepared by dc magnetron sputtering technology.The thickness independence of MA was obtained by observing a series of hysteresis loops and magnetic domains.Then,comparing CoFeB films with grown at magnetic field or not,we did a series of ferromagnetic resonance experiments to obtain magnetic anisotropy quantificationally.The MA is proved subtly to be related to the variation of orbital magnetic moment acquired by ferromagnetic resonance.Furthermore,we found atoms come together into clusters and tend to have order in amorphous CoFeB thin films with field-induced MA by structural and valence state characterization.Based on these experimental results,we proposed a direction-like order model to interpret the origin of magnetic field-induced MA in amorphous CoFeB thin films well.2.The direction-like order model we proposed can explain the origin of magnetic field-induced MA in Co films.After using dc magnetron sputtering technology to deposit films,there was a quite significant magnetic field-induced uniaxial MA appeared in Co thin films containing single ferromagnetic atoms.The Co films were deposited with H_growapplied along different in-plane direction and characteristed to obtain hysteresis loop,which can further discuss the relationship between Co magnetocrystalline anisotropy and MA induced by magnetic field.Then,we analyzed the effect of buffer layer or covering layer to MA.In addition,we did a number of structural characterization,and find these samples own poor crystallinity with MA induced by magnetic field and their atom arrangement incline to order,which can be explained by direction-like order model.The next,we annealed these samples with MA induced by magnetic field at proper temperature,which break original atom arrangement,then Co film grown in magnetic field restored magnetic isotropy.Therefore,our model can explain the origin of magnetic field-induced MA in these films.