The Modulation On The High-frequency Soft Magnetic Thin Films Based On Exchange Bias

In recent years,the electronic industry has developed rapidly.Magnetic materials have a great market demand as an important component of electronic components.CoFe alloys have a more than 20 kG saturation magnetization in ferromagnetic alloys.It can obtain high frequency microwave permeability.Besides,it have many advantages over other soft magnetic thin films.However,only the magnetic anisotropy field from 10Oe to 40Oe can determine the ferromagnetic resonance frequency.It is difficult to achieve a high permeability and resonant frequency at the same time.In an anti-ferromagnetic?AFM?/ferromagnetic?FM?soft-magnetic film architecture,the exchange bias field generated by AFM/FM can significantly increase the anisotropy field soft magnetic films.Which can be utilized to improve frequency.Therefore,the high-frequency characteristics of CoFe/IrMn multilayer films were explored in view of this idea.And the modulation on high-frequency thin films was achieved by combining the semi-pinning structures and full pinning structures.The use of different exchange bias field FM/AFM bilayer system to prepare a soft-magnetic film with high frequency characteristics.Which is beneficial for the preparation of multi-absorption spectrum thin film noise suppressor basis.Following is the specific research content:In this paper,we started studying the aspects of CoFe alloy films from composition,surface morphology,crystal texture and so on.It was found that the optimum high-frequency soft magnetic properties can be obtained in the CoFe thin film under ultra-low sputtering pressure by changing the sputtering pressure.Secondly,the influence of ferromagnetic and anti-ferromagnetic films on the exchange bias field in CoFe/Ir Mn exchange bias system was studied.The relationship between exchange bias field and the thickness of magnetic layer was determined.It was found that anti-ferromagnetic layer is beneficial to improve the magnetic anisotropy of the films.The anisotropy is inversely proportional to the thickness of the ferromagnetic layer in the range of 10 nm to 40 nm,which lays the foundation for the frequency modulation on the thin films.The high-frequency soft magnetic multilayer films were studied based on the exchange bias principle.The single peak resonant peak position of the high-frequency soft magnetic films can be effectively modulated by utilizing half-pinning structure or full-pinning structure.The best high-frequency thin film was obtained when Cu?5nm?/[IrMn?15nm?/CoFe?40nm?/Ir Mn?15nm?]₃ was prepared in the full-pinning structure.The resonant frequency was 3.54GHz and the full width at half maximum was1.96 GHz.Finally,the modulation can studied by changing the thickness of the underlying ferromagnetic layer or the thickness of the top layers.Changing the thickness of the underlying ferromagnetic layer can achieve modulation of the low frequency peak when the composition and thickness of the top layer sample are fixed.The magnetic spectrum curve appears as a single peak when the thickness of the underlying ferromagnetic layer CoFe layer is less than the thickness of the top magnetic layer.The low frequency peaks decrease as the thickness of the bottom layer increases when the thickness of the underlying magnetic layer is greater than the thickness of the top magnetic layer,Which can modulate the low frequency peaks from 3.11 GHz to 2.24 GHz.Similarly,changing the thickness of the ferromagnetic layer in the top-level can modulate on the high frequency peaks.Therefore,a multi-band adjustable thin-film electromagnetic noise suppressor can be realized by using the thin films.