Preparation And Performance Study Of High Properties NdFeB Micron Films

For Nd Fe B films used in magnetic MEMS,the thickness needs to reach the micron level（>5μm）.However,micron-thick Nd Fe B films still have problems such as low magnetic properties and film shedding.In this paper,Si/Ta/Nd Fe B/Ta monolayer micron films were prepared by ultra-high vacuum magnetron sputtering system,and the effects of different target material composition,deposition process and annealing conditions on the structure and magnetic properties of the film were studied.By increasing the thickness of the Nd Fe B layer,a strong anisotropic Nd Fe B film with a thickness of 9μm was prepared.The effect of buffer layer thickness on inhibiting the shedding of Nd Fe B micron films was also explored.XRD,SEM and EDS were used to analyze the phase composition,microstructure and element distribution of thin films.PPMS and MFM analyzed the magnetic properties and domain morphology of the film.Glow discharge emission spectroscopy was used to analyze the elemental composition of thin films with thickness.The results of this study are as follows:（1）Si（100）/Ta（100 nm）/Nd_11.35Fe_76.55B_12.10-Nd（1μm）/Ta（100 nm）films were deposited by co-sputtering with Nd targets.With the increase of nominal Nd content,film coercivity increases,but excessive Nd content will lead to the deterioration of film anisotropy.（2）Magnetron sputtering prepared Si/Ta（100 nm）/Nd_xFe_91-xB₉（x=14.5,16.4,18.2）（2μm）/Ta（100 nm）films;The results show that with the increase of the Nd content of the target material,the coercivity of the film increases.When x=14.5,the film obtains a higher anisotropic tissue,but the film coercivity is low.At x=18.2,the film has high coercivity but reduced residual magnetism,and the tissue tends to be isotropic.At x=16.4,high coercivity is obtained with better vertical anisotropy.（3）By increasing the thickness of Si/Ta（100 nm）/Nd_16.4Fe_74.6B₉/Ta（100 nm）films.From2μm to 9μm,the coercivity,remanence and saturation magnetization strength did not decrease,and more importantly,the texture of the film did not deteriorate,and the successful preparation of strong anisotropy was achieved.The in-situ annealing temperature was increased to 800°C,and the magnetic energy product increased to 28.1 MGOe.By increasing the thickness of Si/Ta（100 nm）/Nd_18.2Fe_72.8B₉/Ta（100 nm）film,the film exhibits isotropy at 140 W,reduces the sputtering power to 100 W,and the film exhibits certain anisotropy.（4）The micromorphology of Nd Fe B films with a thickness of 7-9μm was analyzed,and the source of high anisotropy of high magnetic properties was the growth of main phase grains along the vertical film surface.During the annealing process,the Ta buffer layer exerts compressive stress on the Nd Fe B layer,forcing the Nd liquid phase to be extruded and redistributed from the capping-surface,which homogenizes the film components and improves the magnetic properties of the film.（5）Under rapid annealing at 850°Cx20 min and 900°Cx20 min conditions,the inhibition of Si/Ta（x nm）/Nd_14.5Fe_74.5B₁₁（6μm）/Ta（100 nm）/Ta（x=100,230,380,500,650,1000）films with the change of thickness of the Ta buffer layer was studied.The experimental results show that increasing the thickness of the buffer is beneficial to inhibit the peeling of the film during the high-temperature annealing process.