Tuning The High-frequency Properties Of Permalloy Film With Stripe Domain

In modern science and technology,electronic components are gradually developing in the direction of thin film,miniaturization,high frequency and integration,and have higher requirements for information processing speed and transmission speed,such as the current fifth generation?5G?mobile communication.The development of technology has put forward higher requirements for high-frequency soft magnetic materials used in it.As the work frequency of electronic components increases,this requires magnetic film with a higher resonant frequency in the GHz band.Although a soft magnetic film with uniaxially anisotropic can achieve a higher resonant frequency,the film only responds to the microwave field in one direction strongly and cannot be altered when the film is fabricated into a microwave device.Therefore,how to tune the microwave response of the soft magnetic film in a wide and multi-azimuth frequency range still has great challenges,and the soft magnetic film with the stripe domain structure can tune the ferromagnetic resonance frequency by changing the direction of the applied magnetic field.Although the stripe domain structure with rotational anisotropy can obtain an adjustable resonant frequency,but in the same resonant mode,it has a consistent response to the microwave field in all directions,that is,the high frequency magnetic properties of the stripe domain film is isotropic.The main research goal of this thesis is to further control the resonant frequency of the stripe domain film in different directions,in addition to the electrical measurement of the stripe domain structure film and the ferromagnetic bilayer film.The main contents are as follows:1?Tuning the FMR frequency of stripe domain film via different methods.In chapter 4,the stripe domain film with an effective uniaxial anisotropy field is obtained by micro-nano processing,oblique sputtering,magnetic field heat treatment,etc.,so even in the same resonant mode,the film has different resonance frequency in different microwave excitation directions.Although the magnetic field heat treatment method does not introduce obvious in-plane anisotropy in the permalloy film,it has a relatively large influence on the morphology,static and dynamic properties of the film.The nanowires arrayed along certain orientations are prepared by electrospinning,and the stray field introduced by the nanowires weakens the stripe domain structure,thereby enhancing the soft magnetic properties of the film.In chapter 5,we have selected the non-metal oxide SiO₂,the rare earth element Dy and the transition metal Zr doped into the stripe domain film.The results show that element doping can tune the resonance frequency and damping factor of the stripe domain film in a small range.2?Since the stripe domain structure re-orientates with varying the applied magnetic field,it affects the detection and analysis of the high frequency magnetic properties of the film.The conventional spin rectified voltage signal is obtained by sweeping the magnetic field.However,this method does not fit for the stripe domain structure.Therefore,in chapter 6,we have proposed a method of swept-frequency to detect SRE DC voltage in the stripe domain structure film,so as to obtain more sample information.In addition,we test the voltage signal of the exchange bias bilayer MnIr/NiFe film,not only the exchange bias field can be easily obtained from the voltage spectrum,but also the resonant and non-resonant SRE signals of this system are analyzed and determined.These two effects are derived from magnetization reversal and ferromagnetic resonance,respectively.Next,we investigate the ST-FMR in the Py/Pt bilayer film based on the spin Hall effect.As the thickness of Pt increases,the spin pumping effect becomes weaker and the damping of the bilayer film is smaller.The spin current is generated by the DC currents flowing the sample,then and causes a damper-like torque to act on the magnetization,which further tunes the damping of the sample.The ratio of spin to charge currentJ_s /J_c can be obtained by the relationship between the resonance width and the DC current.