The Research On Magnetic Properties Of MgCuZn Ferrite Applied For NFC System

NFC?Near Field Communication?technology evolved from radio frequency identification?RFID?and interconnect technology to identify and exchange data with compatible devices in a short distance.Currently the NFC technology is being rapidly developed,but the near-field noise source in near-field wireless communication system is detrimental to the safety,stability and sensitivity of the system.Soft magnetic shielding materials,which is able to shield the near-field noise sources,are widely used in NFC systems.This paper is aimed at the high permeability and high quality factor of MgCuZn ferrite material at 13.56MHz.MgCuZn ferrite was prepared by solid state reaction method,and the goal was achieved by monodomain design.The effects of monodomain design,ZnO content and additive on the microstructure,magnetostatic parameters and magnetic properties of MgCuZn ferrite were studied in details.The main results are as follows:1.The effect of single domain design on the magnetic properties of MgCuZn ferrite material was studied.Firstly,the effects of calcination temperature on the grain size and magnetic properties of MgCuZn ferrite were discussed.The experimental results show that the proper calcination temperature is 900?,which is beneficial to make the powder have higher activity and obtain more ideal micro-morphology and magnetic properties.Then,the influence of monodomain and multi-domain structure on the magnetic properties of MgCuZn ferrite was analyzed by using the magnetization mechanism of ferrite.On the basis of the analytical method,the effect of microstructure on the magnetic properties of monodomain Experiments show that grain size control under the critical domain size will be able to obtain MgCuZn ferrite with high quality factor.2.The effect of different ZnO contents on the magnetic properties and microstructure of ferrite materials were analyzed.It is concluded that the proper increase of the content of ZnO in the formula can greatly improve the Snoek limit of the material.According to the design specification,the stoichiometry with the greatest application potential is obtained.3.On the basis of the stoichiometr with the largest Snoek limit,the influence of CoO additive on the microstructure and magnetic properties of monodomain MgCuZn ferrite was investigated.The experimental results show that the introduction of Co ions improves the cutoff frequency and the quality factor,and reduces the magnetic loss of the material.The influence of CoO on the magnetic spectrum of monodomain MgCuZn ferrite is further revealed by magnetic spectrum fitting.The magnetic spectrum is mainly determined by the static magnetic domain rotation susceptibility K_s,the magnetic domain rotation resonance frequency?₀ and the relaxation frequency?_r.The results show that with the increase of CoO addition,K_s decreases and?₀ increases,and?_r is a segmentation function with frequency f as a variable.Finally,the magnetic properties were obtained by the regulation of CoO addition.The real part,imaginary part and quality factor of the magnetic permeability of the sample at 13.56MHz are 159.44,2.91and 54.79 respectively.