Orientation Growth And Adjustable High Frequency Magnetic Properties Of Alloy Soft Magnetic Film With Negative Magnetic Crystal Anisotropy Constant

In recent years,study of soft magnetic thin films?SMTFs?has become one of the hot topics in the field of magnetism because of their potential applications for electronic equipment in high-frequency fields,such as miniature inductors,micro-transformers and noise suppressors.In practical applications for SMTFs,it is required to not only have good comprehensive properties,such as high saturation magnetization,low coercivity,high permeability and high natural resonance frequency,also have a sufficient thickness?usually above micrometer?to obtain enough magnetic flux signal.At present,the well-studied Fe-and Co-based amorphous and nanocrystalline SMTFs have excellent static and high-frequency magnetic properties.Due to Acher limit,the natural resonance frequency cannot be further improved with the unchanged initial permeability.And due to defects and/or internal stress coming from the film growth procedure,considerable perpendicular anisotropy will always occur and result in the appearance of the stripe-type domain structure when the thickness of these SMTFs exceeds a few hundred nanometers.This not only reduces soft magnetic properties of these SMTFs,but also limits magnetic flux signal.However,Acher limit is an obstacle for the c-axis oriented CoIr SMTFs.Because of negative magnetocrystalline anisotropy,the natural resonance frequency of CoIr SMTFs will be greatly increased while the initial permeability does not decrease.In addition to the demagnetization field,the rotation of magnetic moments from the c-plane to the c-axis direction must overcome large effective magnetic field.Therefore,the transition thickness from Néel wall to Bloch wall is dramatically enhanced.However,further regulation of high frequency magnetism,further optimization of soft magnetic properties,and whether the stripe-type domain will occur still need to be explored.In addition to CoIr alloy,there are a number of rare earth alloys with stronger negative magnetocrystalline anisotropy than CoIr alloy.We expect to prepare rare earth soft magnetic film by magnetron sputtering technology.Therefore,this paper further optimized the magnetic properties and regulated the high frequency magnetism of CoIr thin films,and preliminarily explored the preparation methods of rare earth alloys by magnetron sputtering.So the CoIr SMTFs and rare earth alloy films are prepared by magnetron sputtering and their properties were measured with XRD,VSM,ESR,VNA and so on.The effects of wedge angle,annealing temperature and different seed layer on the c axis orientation growth,optimization of the magnetic properties and regulation of high frequency magnetism are studied for CoIr thin films.For the hcp-?CoIr?_100-xM_x?M=Cr,B,SiO₂,Ni?SMTFs,the orientation growth and regulation of high frequency magnetism are studied with increasing x.The micrometer thick soft magnetic films have been fabricated,and the c axis orientation,magnetic moment distribution and microwave properties are discussed.The preparation of rare earth soft magnetic films by magnetron sputtering is discussed and summarized.The main results are as follows:?1?Adjusting in-plane uniaxial anisotropic field.With the wedge angle increasing,the in-plane uniaxial anisotropic field can be controlled and the high frequency properties can be adjusted conveniently.Moreover,the c axis orientation degree and total out-of-plane anisotropy field are not deteriorated.?2?Adjusting the out-of-plane anisotropic field.With the increase of annealing temperature,both ESR and VNA test methods show that the out-of-plane anisotropic field first increases and then decreases.The high frequency propertie can be improved with annealing temperature.While the crystal structure is broken by higher temperature and the properties are reduced.?3?Adjusting orientation growth of CoIr thin films.The oriented seed layer?Ni,Cu,Ir,Pt,Au?can induce the magnetic layer to grow along the c axis,while the film without seed layer has poor orientation.The soft magnetic properties,out-of-plane anisotropic field and intrinsic magnetocrystalline anisotropy are also sensitive to the geometry and size of the underlying lattice.The initial permeability is not related to the seed layer,while the natural resonance frequency is strongly restricted by the material and structure of seed layer.?4?Optimizing the properties of CoIr films.A series of c-axis oriented hcp-?CoIr?_100-x00-x M_x?M=Cr,B,SiO₂,Ni?SMTFs are successfully prepared.The Cr and Ni atoms reside at the interspace of different grains and/or successfully enter into the crystal structure,while the crystal structure became unstable and eventually the film became amorphous with large number of B and SiO₂dopants.These dopants can greatly optimize the soft magnetic properties in within certain range and affect the negative magnetocrystalline anisotropy.As expected,microwave properties can be tuned subsequently in a wide range to meet specific requirements of different applications.?5?Studying the properties of c-axis oriented micrometer thick soft magnetic films.The perpendicular anisotropy increases with the increase of film thickness,and is about 250 kJ/m³when micrometer thickness.While the negative magnetocrystalline anisotropy is about-753 kJ/m³,and the net magnetic anisotropy is still negative.The magnetic moments lie strictly within the film plane for micrometer thick films.?6?Prospecting rare earth soft magnetic films.The preparation methods of rare earth alloys with higher negative magnetocrystalline anisotropy by magnetron sputtering is explored,and the preparation process and test results are summarized.On this basis,some suggestions easy operating are put forward for successful preparation of rare earth soft magnetic films.For example,adding temperature of the substrate and sudden cooling the thin film sample.By fine tuning the growth condition or annealing process,we can change the defect and internal stress of the film to control the magnetostatic parameters and adjust the high-frequency magnetic properties.By adding a third component during the film growth process,we can refine the grain and reduce the internal stress to achieve the same goal,and to optimize the soft magnetic properties.Due to negative magnetocrystalline anisotropy,the magnetic moment of the micron thick CoIr film is limited within the plane,and the rare earth alloy soft magnetic film will be an ideal material with higher microwave properties.