The Study Of The Magnetic Properties Of Ni - Zinc Ferrite Thin-film High Frequency

Ni-Zn ferrite material with high resistivity, high permeability, resonant frequencyand low loss tangent is good for the high-frequency application. With the developmentof miniaturization, integrated and high frequency of electronic devices, the study of theNi-Zn ferrite thin-film material becomes the key point. In this dissertation, thepreparation process of Ni-Zn ferrite thin films and its high-frequency magnetic propertywere studied. The main contents include:Firstly, Based on the Monte Carlo method, the effect of incident particle energyand the incident angle on the sputtering yield and outgoing atomic weight ofNi0.5Zn0.5Fe₂O₄ferrite target was studied. The results show that: The sputtering yield ofeach element of the target is gradually increasing with the increasing incident energy inthe vertical incident angle; The sputtering yield of each element of the target increasesfirst and then decreases with the increasing incidence angle in the5KeV incidentenergy.Then, Ni0.5Zn0.5Fe₂O₄ferrite thin film was prepared by means of RF magnetronsputtering, the influence of thickness of thin film, oxygen partial pressure, substratetemperature and the added buffer layer on the phase, microstructure, the static magneticproperties and high-frequency performance of Ni-Zn ferrite thin film has been studied.It shows that:（1）As the thickness of the film increase, grain size and the film surface roughnessincrease, and the saturation magnetization（Ms） and coercivity（Hc） increase slightly.When the film thickness reaches2.25μm, Msand Hcreached the maximum. In thehigh-frequency magnetic property, the real permeability at1GHz gradually increased.The scope that the imaginary part of complex permeability of the sample is greater than50is expanding, and the scope of frequency moves to the higher frequency when thefrequency is higher than0.31GHz.（2）With the increase of oxygen partial pressure, the grain size decreases. Inmagnetic properties, both Msand μ’ increases first and then decreases. When the oxygenpartial pressure is15%, Msand μ’ reaches the maximum,412KA·m-1,200, respectively. Contrary to the variation of μ’, when the oxygen pressure is15%, cutoff frequency （fr）reaches0.52GHz. Hcincreases slowly after initial rapidly increase with the increase ofoxygen partial pressure, when the oxygen pressure is20%, Hcreaches the maximumvalue （10.8KA·m-1）.（3）As far as the unannealed film concerned, with the increase of substratetemperature, the diffraction peak intensities of the sample increase, the orientation of thefilm is better, Msincreases and Hcdecreases; About the annealed films, the grain sizeincreases, and contrary to Hc, Msincreases first and then decreases with the increasingsubstrate temperature. Msand Hcreaches the highest value（242KA·m-1） and the lowestvalue（6.39KA·m-1）, respectively, when the substrate temperature is250℃. In the aspectof high-frequency performance, μ’ and frincreases and decreases gradually withincreasing substrate temperature.（4）Buffer layer of ZnFe₂O₄ferrite effectively prevent the inter-diffusion betweenthe substrate and the deposited layer, induces the growth of Ni-Zn ferrite thin films,increases intensity of the deposited film diffraction peak, and makes crystal particle sizeuniform. So Ni-Zn/ZnFe₂O₄ferrite films whose Ms,Hcand μ’ reaches390KA·m-1,5.69KA·m-1and225respectively is got, but the introduction of the buffer layer hasnothing to do with the increase of frof NI-Zn ferrite thin film except the decrease ofpermeability.