Investigation On Measurement Method For High Frequency Permeability Spectra Of Soft Magnetic Films And Its Application In The Permalloy Films

Recently,with the rapid development of social economy and the improvement of life quality,People has higher requirement for high-tech products,which promotes the rapid development of electronic technology and components,especially,in the direction of miniaturization,thin film,integration and high frequency.Taking the communication frequency band as an example,the early frequency of communication system is 900 MHz and 1.8 GHz,namely,GSM standard or the second generation(2G).The current frequency of communication system has been promoted to 3 GHz and 4 GHz.This puts forward higher requirements for the magnetic functional materials.Soft magnetic materials have attracted much attention due to its application in the inductance and transformer.With the increase of working frequency of the components,it requires the magnetic thin films have excellent high frequency properties,such as higher permeability value and high resonance frequency.Hence,how to measure the high frequency performance of the magnetic film is one of the important issues in this field to be solved urgently.This thesis is mainly around the measurements and evaluation of the high frequency performance of magnetic films.Based on the research and comparison on the measurement method of high frequency performance of magnetic film,we proposed an induction method to measure the high frequency performance of magnetic film without a standard sample.Besides,we investigated the properties of the Permalloy films.The main content of this thesis is shown as follows:1.We summarised the measurement methods of high frequency performance of magnetic film by using the shorted microstrip line,and then improved them.We designed and assembled the microstrip line jig by using the Ansoft HFSS software,and achieved the broadband measurements of the complex permeability of magnetic film by optimizing the dimensional parameters of the jig and the instruments parameters.What's more,we proposed an induction method to measure the high frequency performance of magnetic film without a standard sample,and we just use the size of the sample in the process of calculations.Besides,we study the rectangular type(Coplanar waveguide,referred to CPW)jig to measure the high frequency performance of magnetic film,and compare with the shorted microstrip line jig.If we apply a DC magnetic field in the measurement process,which means that the ferromagnetic resonance can be measured by vector network analyzer(VNA),it can be called VNA-FMR method.2.We used the top-down method to prepare the Permalloy films with different thickness.By using the vectoe network analyzer ferromagnetic resonance(VNA-FMR)method,we studied the high frequency performance of stripe domains in the Permalloy film when the excitation is along the parallel direction and perpendicular direction.For the dynamic pseudo-uniaxial anisotropy fields along the stripe direction,we studied the origin by building a simple physical model.In addition,we studied the rotation properties of the stripe domains via the MFM and VNA-FMR method.We also studied the angular dependence of the high frequency performance of stripe domains.By establishing a phenomenological physical model,we obtained a relationship between the initial permeability value and rotation angle,which can be used to evaluate the average value of the periodic function of the anting angle ? in a periodic stripe.What's more,we studied the annealing influence on the stripe domains structure in Permalloy films by comparing the static and dynamic magnetic properties.The results show that the width of stripe domain increases with the increase of annealing temperature,meanwhile,the coercivity and the permeability are also increase.It proves that the annealing enhances the exchange stiffness constant by using the Herzer model,VNA-FMR results,and micromagnetic simulation.3.We investigated the static and high frequency dynamic performances of the surface FeCo disks modified Permalloy films by using VNA-FMR method.The results show that whether the square arrays are used,the surface modification with different disk density can slightly tailor the damping parameters from 0.008 to 0.013 by controlling magnetic field.This is significant for the practical applications.In addition,we also studied the high frequency performance of the Permalloy film with anti-disks by the VNA-FMR method,and the results show that the anti-disks structure has various resonance modes.4.We try to control the ferromagnetic resonance of Permalloy films via the electrical method based on the spin Hall effect(SHE).Firstly,the spin pumping effect in the Pt/Permalloy film was studied by using VNA-FMR method,which exhibits that the spin current can inject each other through the interface of the samples we prepared.Then,we measured the complex permeability of Pt/Permalloy film,and provided a direct current to the sample at the same time.The results show that this electrical control method based on SHE can tailor the damping parameters of the Permalloy film in a small degree.