Research On High Frequency Soft Magnetic Film And Its Frequency Control

In the information age,electronic components are trend to be 2D planar and integrated.Microwave soft magnetic films are widely used in monolithic microwave integrated circuits because they can effectively reduce the dimension of electromagnetic components and devices,such as filters,micro-magnetic inductors,antennas and so on.Practically used soft magnetic films should exhibit high permeability?,high ferromagnetic resonance frequency1)_FMR in self-bias condition?magnetic field free?and an integrated circuit?IC?compatible fabrication process.Because the working frequency of electromagnetic equipment is limited by the ferromagnetic resonance frequency of magnetic materials,it is the most important to enhance the ferromagnetic resonance frequency of microwave soft magnetic films.Firstly,in this thesis,Fe_0.5Co_0.5-ZnO films with high resistivity were fabricated by a compositional gradient sputtering on?011?lead zinc niobite-lead titanate?PZN-PT?substrates.It is interesting to note that the resistivity of the ZnO-doped Fe_0.5Co_0.5 films is10-30 times larger than that of pure Fe_0.5Co_0.5 films.An ultrahigh1)_FMR of 10.48 GHz were achieved at electric field of 8 kV/cm without bias magnetic field.The excellent microwave ferromagnetic performances in as-deposited films can be attributed to two reasons:?1?the large uniaxial anisotropy field induced by gradient composition of doping ZnO,?2?the strong magnetoelectric coupling between the ferromagnetic/ferrielectric interfaces under the condition of high resistivity in Fe_0.5Co_0.5-ZnO films.Secondly,Fe_0.5Co_0.5-MgO films with MgO-doping content exceeding its solubility in FeCo alloy,were fabricated by a composition gradient sputtering on?011?lead zinc niobate–lead titanate?PZN-PT?substrates.A nanogranular structure of the films due to the excessively doping leads to a dramatic increase of resistivity over 20 times than the pure FeCo films.As a result,a large self-bias?without external magnetic field,H=0 Oe?ferromagnetic resonance frequency1)_FMR of up to 9.87 GHz with an electric field tuning frequency range of 0-4.55 GHz,were achieved in the as-deposited films at electric fields of 0-7 kV/cm.Both high resistivity and high1)_FMR in Fe_0.5Co_0.5-MgO/PZN-PT heterostructures provide a great opportunity to apply in self-bias tunable monolithic microwave integrated circuit?MMIC?devices.Finally,Y₃Fe₅O₁₂ target with positive proportion of yttrium oxide and iron oxide was prepared by solid phase sintering.Then Y₃Fe₅O₁₂ thin film samples with 200 nm thickness were deposited on GGG substrates with different crystal orientations by pulsed laser deposition?PLD?.The appropriate growth pressure and magnetic properties of thin film samples with different orientations were investigated.YIG/Ta/YIG thin films were prepared.It was found that the insertion of tantalum in the middle layer increased the ferromagnetic resonance frequency of the thin films.It was also found that the increment of the frequency changed periodically with the in-plane measurement angle of the samples.The increase of the frequency in the direction of easy magnetization axis was significantly greater than that in the direction of difficult axis,suggesting that a magnetocrystalline anisotropy dominated magnetic anisotropy is present.