Preparation And Magnetic Characterization Of FeCo Alloy Thin Films

With good soft magnetic properties of the high saturation magnetization,low coercivity,high permeability and good thermal stability,Fe Co alloy thin film has become one of the intensive researches.It is because of these good soft magnetic properties that FeCo thin film has been widely applied in magnetic recording,microwave absorbing,generator materials.At present,there are a lot of methods to prepare FeCo thin film,such as electrochemical,chemical vapor deposition,Sol-gel,Plasma deposition,physical vapor deposition and so on.In this paper,we use physical vapor deposition which has advantages of controllable deposition rate and parameters,simple operation.Next,we analysis the films’structure and magnetic property by XRD,SEM,VSM,XPS.In this work,firstly,we apply co-sputtering to prepare FeCo alloy thin films,the magnetic properties of FeCo alloy films were studied from different atomic ratios and different annealing temperatures.In order to change Fe,Co compositions,different Fe sheets were pasted on Co target.The experimental result showed that:with the increasing of Fe composition,the saturation magnetization increased from 1284 emu/cc to 1587 emu/cc.As to annealing temperature,the coercivity increased with annealing temperature before 600℃while it decreased after 600℃.And the saturation magnetization grew all the way when annealing temperature grew.Especially,Fe₅₁Co₄₉ obtained the best magnetic properties and thermal stability in this work.Then we analyzed FeCo alloy thin film through XPS and EDS,we found that Si atoms in the substrate and Fe,Co atoms in the film would diffuse mutually,besides,Si and Fe atoms formed FeSi structure,and FeSi structure ratio improved while the saturation magnetization reduced when annealing temperature grew,at the same time,high annealing temperature also made flatness and uniformity reduce.Secondly,the incorporation of N in FeCo alloy films can effectively reduce the size of alloy particles,thereby enhancing the soft magnetic properties of FeCo alloy films.Hence,in this paper,we incorporated argon nitrogen mixture in the process of preparation,and controlled the pressure of gas to control the proportion of N elements in the film.The magnetic properties of FeCo alloy films were studied from proportion of N elements and different annealing temperatures.Four experiments were carried out to investigate the effect of N content on the magnetic properties of FeCo alloy films with 6%,12%,17%and 21%N contents.The experimental result showed that:because N atoms combine Fe,Co atoms to formed Fe N,CoN phase,FeCo phase declined even disappeared.The coercivity and magnetic saturation of(Fe₅₁Co₄₉)N_0.06 was 465 Oe and 1540 emu/cc respectively,when it was 652 Oe and 1606 emu/cc without N.As the proportion of N further increased to 17%,The coercivity and magnetic saturation of(Fe₅₁Co₄₉)-N_0.17 declined to 221 Oe and 1192emu/cc.Both coercivity and saturation magnetization decreased with increasing N content.As to the annealing temperature,the coercivity and saturation magnetization increased with the growth of the temperature before 600℃,but when the temperature exceeded 600℃,the magnetic domain of the film changed and the coercivity reduced.