Investigation On The Preparation Of YIG Ceramics Used For PLD And Micron-grade YIG Films

With the evolution of modern communication technology,the microwave ferrite devices,such as circular,phase shifter and isolator etc,which used in communication system core part plays a more and more important role in mobile communication.In numerous ferrite materials,yttrium iron garnet(YIG)is widely used because of its good spin magnetic,small resonance linewidth and low dielectric loss.Currently,the miniaturization of the device has become an inevitable trend of microwave devices development with the development of monolithic microwave integrated circuit(MMIC).Therefore,how to poduce the high quality YIG films which meet the requirements of thin film devices is worth of further research.This study focused on YIG bulks used for PLD(pulsed laser deposition)and micron-grade YIG films prepared by PLD technique.Study on YIG bulks is the foundation of the study on YIG films.Effect of different preparation modes on the surface morphology,microstructure,crystallinity and magnetic properties was studied.Firstly,YIG bulks were prepared by two-step sintering.Effect of the first-step sintering temperature(T1),the sintering temperature sintering(T2)and the holding time on the YIG bulks were investigated.The results indicated that the TSS process can effectively suppress grain-boundary migration while maintaining active grain-boundary diffusion.The sample prepared by the TSS process with T1 of 1350 oC,T2 of 1300 oC,and holding time of 18 h had high density and exhibited uniform microstructure with small average grain size(2.4?m).The saturation magnetization(MS)of this sample reached 27.4emu/g.Secondly,the YIG bulk was used as the target when micron-grade YIG films were prepared on GGG substrate by continuous deposition method using PLD device.Effect of annealing temperature on the properties of micron-grade YIG films was explored.The results showed that the film has the best performance in terms of surface morphology,roughness and crystallinity when the annealing temperature was 750 oC.The film with maximum thickness of 7?m was obtained at the annealing temperature of 750 oC by continuous deposition method.The ferromagnetic resonance linewidth and Ms of the film are 35 Oe and 152emu/cm3,respectively.Eventually,the YIG films were prepared on GGG substrate by layer-by-layer deposition method.The YIG films of different thickness were respectively prepared under 1+3+3+3...mode(3?m thick films were deposited each time)and 1+1+1+1…mode(1?m thick films were deposited each time).And the relationship between the thickness and the properties of films was explored.The film with maximum thickness of 10?m was prepared under 1+3+3+3...mode.The ferromagnetic resonance linewidth and Ms of the film are 60 Oe and 190emu/cm3,respectively.And,the film with maximum thickness of 13?m was prepared by the layer-by-layer method(1+1+1+1...mode).The ferromagnetic resonance linewidth and Ms of the film are 23 Oe and 148emu/cm3,respectively.