Study On High Frequency Electromagnetic Characteristics Of Patterned Soft Magnetic Films

With the rapid development of radar detection,communication technology and consumer electronics,high-frequency microwave absorption characteristics of magnetic materials in the microwave band are widely used in military and civilian fields.For example,in modern wireless communication,we use the mobile phone to carry out network communication.All of these require electromagnetic waves for signal transmission.From the development of the past second-generation GMS digital communication to the current fourth-generation 4G communication technology,high frequencies of electromagnetic waves are not only required,but also a need for low signal interference among highly integrated electronic devices.The thin-filmed microwave magnetic material with magnetic anisotropy can greatly optimize the resonant frequency and magnetic permeability,so that the electromagnetic wave can be transmitted faster.At the same time,the problems,such as conducted interference and electromagnetic compatibility interference in the device,can be effectively reduced.Therefore,regulating the high frequency magnetic properties of the material by adjusting the magnetic anisotropy field has become a research hotspot of the thin film material.Since additional shape anisotropy properties are introduced in the graphical cell,the research of patterned films has attracted more and more interest.The focus of this work is on how to prepare patterned films,change the size of the patterning unit,and mix the arrangement way to introduce the shape anisotropy property to achieve effective control of the high-frequency magnetic properties of NiFe soft magnetic films,and further to arrive the purpose of high-frequency,integration,fragmentation,and miniaturization in deceives.The main contents are as follows:?1?The different widths of NiFe soft magnetic film micro-stripes are fabricated by the photolithography and magnetron sputtering techniques,in which the designed line width changes from 2?m to 30?m.Compared with the continuous film,The patterned film sample shows a significant shape magnetic anisotropy which Increase from 87 Oe to 576 Oe as the line width decreases.The related resonance frequency of the sample increases from 0.7 GHz to 10.6 GHz,and it realize the controllable changes in the four bands L,S,C,and X.?2?The 15?m and 30?m micron-sized magnetic strips are mixed and arranged on a 5×5 mm substrate in different proportions.After the different magnetic stripe is assembled,the coercive force of the easy axis of the hysteresis loop increases,the in-plane magnetic anisotropy H_k decreases,and the loop shows a step structure which is likely to the stripe domain loop.The MFM image shows that the internal domain structure of the magnetic-stripe is rearranged.The resonant frequency of the sample after the combination is increased to 7 GHz and the magnetic permeability keeps a high value breaking the traditional Acher limit.?3?The Al₂O₃ substrates were heat-treated at different temperatures.The wavelength and peak height of similar triangular wave pattern formed on the surface of the Al₂O₃ substrate was characterized by MFM.As the temperature increases,the wavelength increases to 62.1 nm,the coercive force of the easy axis of the hysteresis loop increases to 75 Oe,and the magnetic anisotropy field formed increases to 238 Oe.It indicates that the introduced nanotriangular wave stripe by the Al₂O₃ substrate heat-treated can affect the magnetic anisotropy of the sample.And compared with a flat continuous film,the resonant frequency of the nanopatterned film increased by a factor of two.