Preparation And Characterization Of Fe-Based Amorphous/Nitride Double Layer Structure

Amorphous Fe-Si-B alloys are the representative with several practical applications in transformers and inductors because of their excellent soft magnetic properties,such as high permeability,low coercivity and low core losses.However,the relatively magnetostriction constant and low saturation magnetization Ms hinder its further performance improvement as soft magnet materials.While the iron-nitrogen compounds,especially a"-Fe16N2,have a large saturation magnetic moment.Based on this,the layer of nitrides was introduced on the surfacc to form the bilayer structure in iron-based amorphous strips by N+ ion implantation.The soft magnetic properties and the magnetostriction constant of the novel strips with bilayer structure are systematically studied.In addition,the effect of rare earth element Yttrium addition on the crystallization behavior and magnetic properties of Fe-based amorphous alloy ribbon was also studied.It is found that the dose of implantation has an important effect on the crystallization behavior and the magnetic properties of the amorphous matrix.When the implantation dose exceeds 5 ×1016 ions/cm2,the a-Fe phase is formed in the amorphous matrix.AES analysis proves the Gaussian distribution of nitrogen ions in the surface layer.The maximum value of N+ concentration exists in 266nm from the surface.With the increase of the dose,the saturation magnetization increases first and then decreases.The amorphous ribbons under the dose of 1 × 1016 ions ·cm-2 exhibited the maximum saturation magnetization(Ms)of 187.9emu/g,which is obviously enhanced compared to 159.1 emu/g of the original sample.Meanwhile,the saturation magnetostriction coefficient(λs)is reduced from 2.92 ×10-5 to 1.72 × 10-5.The depth of N+ increases with the increase of the accelerating voltage,and the accelerating voltage affects the coercivity and magnetostrictive properties.According to the software simulation results,the distribution of nitrogen ions correspond with Gaussian distribution,and the depth of N+ increases with the increase of the acceleration voltage.When the dose is 1 × 1016 ions/cm2,the amorphous matrix is still maintained in the range of 90-180 kV.With the increase of the acceleration voltage,the coercivity decreases first and then increases.The coercivity of the sample with accelerating voltage of 90kV reaches minimum of 10.35A/m.The change of the acceleration voltage also causes the magnetostriction coefficient to change,and the saturation magnetostriction coefficient of the sample with accelerating voltage of 120kV is 8.4 × 10-6.The addition of rare earth element Yttrium can improve the thermal stability and the magnetic properties of Fe-Si-B amorphous alloy.The initial crystallization temperature increases with the increase of Y content.When the addition amount is more than lat%Y,crystallization behavior of the amorphous changes from two-step into three-step crystallization.It can be attributed to appearance of the metastable Fe3B phase.Furthermore,the addition of rare earth element yttrium can also improve soft magnetic properties of amorphous alloy.With Y addition increases the saturation magnetic moment increases first and then decreases,and the saturation magnetic moment reaches the maximum of 187emu/g at 1.5at.%Y,and the coercivity decreases to 7.6A/m.