| In the fields of extremely weak magnetic analysis,biological magnetic field measurement of human body,and so on.the measurement sensitivity of magnetometers is required to be higher and higher.Spin-exchange Relaxation Free(SERF atomic magnetometer)is the most sensitive magnetometer at the moment,and the measurement sensitivity can reach the magnitude of fT.In order to implement the ultra-high sensitivity of SERF atomic magnetometer,magnetic shielding device is applied to shield the external magnetic field.Currently,1J85 alloy(Ni80Fei5Mo5,NiFeMo)with high permeability is commonly used as passive shielding material,which can weaken the magnetic field to nT magnitude.However,Johnson current will be generated due to its low resistivity,which will generate magnetic field noise and become an important factor limiting the further improvement of sensitivity of SERF atomic magnetometer.As for competitive problem with the increase of resistivity and the decrease of soft magnetic properties in NiFeMo materials,this paper proposes to add insulating medium to NiFeMo film to prepare NiFeMo-SiO2 co-deposition and composite-growth thin films,and changes the content of insulating medium and magnetic particle size to regulate the magnetic properties.In this paper,magnetron sputtering method is adopted.Firstly we study the influence of deposition conditions such as sputtering power,sputtering pressure,film thickness and substrate temperature on the surface micromorphology and magnetic properties of NiFeMo films,and determine the effect of growth conditions on saturation magnetization,coercivity and remanence ratio.Then,during NiFeMo-SiO2 co-deposition,the influence of SiO2 content on surface morphology,microstructure and magnetic properties was studied,to determine the relationship between SiO2 content and magnetic properties.Finally,the mechanism of magnetic particle size increasing saturation magnetization,remanence ratio,reducing coercivity and in-plane anisotropy during composite-growth was studied to reveal the mechanism of regulating the magnetic properties of NiFeMo-SiO2 through microstructure.The main conclusions are as follows:(1)In order to obtain the best magnetic properties of NiFeMo films,the effects of growth conditions on the magnetic properties of NiFeMo films were studied.The results show that with the sputtering power increasing,the deposition particle energy increases,and the soft magnetic property improves;Substrate temperature does not change the phase composition of the film,but it will increase the orientation of FeNi3(111)direction.At 260℃,the coercivity of the film is the minimum(Hc=20.39 Oe),with the remanence ratio and saturation magnetization being the maximum.With the increase of thickness,coercivity and hysteresis loss decreases;Sputtering pressure has a significant impact on magnetic properties.The coercivity(Hc=2.70 Oe)of the film at air pressure of 0.3 Pa decreases by 6.5 times compared with that at 0.5 Pa(Hc=20.39 Oe),while the saturation magnetization and remanence ratio increase.(2)In order to improve the resistivity of NiFeMo films,the influence of SiO2 content in NiFeMo-SiO2 co-deposited films on the magnetic properties was studied.The results show that SiO2 can improve the resistivity and remanence ratio of the film,and meanwhile reduce the saturation magnetization and coercivity of the film.Compared with NiFeMo,when SiO2 content is 12.67vol.%,the saturation magnetization of codeposition film(Ms=392 emu/cm3)decreases by 30.12%,the resistivity increased from 76.5 μΩ·cm of to 359 μΩ·cm,and coercivity reduced from 35.305 Oe to 1.011 Oe.(3)In order to obtain the best magnetic properties of NiFeMo-SiO2 films,the effect of particle size of NiFeMo-SiO2 composited films on the magnetic properties was studied.The results show that SiO2 with low surface energy diffuses to the boundary of NiFeMo to form particle film,which can control the size of NiFeMo particles longitudinally.The order of particle film is inversely proportional to the resistivity,The 83-Period film particles are disordered and have a maximum resistivity of p=740 μΩ·cm.The 17-Period film has a uniform particle size,neatly arranged,and have a minimum resistivity of ρ=196 μΩ·cm.Larger grain size favors the increase of saturation magnetization.The 17-Period film has the highest saturation magnetization(Ms=491 emu/cm3),which is 24.74%higherthan the saturation magnetization(Ms=392 emu/cm3)of SiO2-12.67vol.%co-deposited film.The shape anisotropy of nanoparticles is negatively correlated with in-plane anisotropy.The particles of the 25-Period film are close to spherical,and the M-H curve also exhibits in-plane isotropic. |
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