Microstructure And Micromagnetism Of Co⁵⁷FeIr Soft Magnetic Films With Easy-Plane Anisotropy

The microstructure of a material determines its macroscopic properties,which is particularly applicable for magnetic materials.Soft magnetic film is the essence in the development of miniaturization and high frequency of electronic devices,and it is also indispensable in magnetic storage.In any case,soft magnetic thin films should be endowed with high plane anisotropy.That is to say,the easy magnetization direction of thin films is in the film plane.In general,the strong demagnetization magnetic field of high saturation magnetized soft magnetic film can meet the application requirements,but it is difficult to avoid the influence of defects and stress in the film growth process,resulting in strong out-of-plane(vertical)anisotropy of the film,which greatly reduces the soft magnetic properties of the film.In practical application,the thickness of the film that caters to the flux signal will reduce the demagnetization of the film,destroying its practical application.The paper attempts to indicate that the c-axis oriented CoIr soft magnetic film with negative magnetocrystalline anisotropy can solve these problems well,because the the strong negative magnetocrystalline anisotropy will further bind the magnetic moment in the film plane,equipping the film with have higher cut-off frequency,greatly increasing the critical thickness of the Neel wall,and vanishing the stripe domain in the micron thickness.CoIr soft magnetic thin films have promising prospects in high-frequency devices,magnetic recording and other fields;on the other hand,it is expectable to further expand the application scope of CoIr soft magnetic thin films with negative magnetocrystalline anisotropy.Hence,how to control the microstructure and micromagnetism of CoIr thin films is still a problem to be solved.In this paper,the effect of hydrogen ion implantation on the CoIr soft magnetic film doped with a small amount of ⁵⁷Fe and the influence of negative magnetocrystalline anisotropy on the magnetic vortex of the nanodisk are studied respectively,and their microstructure and magnetic properties were explored with the following conclusions.(1)Hydrogen ion implantation experiments were carried out on hcp-Co₈₀⁵⁷Fe₄Ir₁₆soft magnetic films to research the defects induced by hydrogen implantation and and their internal relationship with macroscopic magnetism.In detail,the low-frequency inductively coupled plasma system is used to generate the required high-density hydrogen plasma.Thereafter the hydrogen ion is implanted into the thin film samples by applying a bias electric field of-60 V?-250 V.Through the procedure of analyzing the samples by XRD,hysteresis loop,complex permeability spectra and Mossbauer spectrum,two types of defects in implanted Co⁵⁷Fe Ir soft magnetic films are disclosed,one of which is non-destructive while the other is destructive.The former is concerned with the hydrogen ion implantation that is proceeded under low bias voltage,where hydrogen ion will embed into the lattice and cause lattice expansion,resulting in a slight increase in saturation magnetization and a slight decrease in coercivity,thus causing negligible effect on high-frequency magnetism.On the contrary,the defects that occurred under high bias voltage are destructive,which will hinder the movement of the domain wall,and increase the coercivity and precession damping constant of the sample.Besides,hydrogen implantation will also evoke the element segregation in the alloy so as to achieve the control of the magnetocrystalline anisotropy of the sample.Briefly,these results provide an original orientation for material processing and a new platform for studying the interplay between different defects and material properties.(2)Based on the existing research results generated in our laboratory,we used the magnetic parameters of the CoIr soft magnetic film as the object of micromagnetic simulation to explore the influence of negative magnetocrystalline anisotropy on the magnetic vortex of the nanodisk.This research is essentially done by micromagnetic simulation,using LLG Micromagnetics Simulator software to simulate the magnetic properties of CoIr alloy under the micro-nano size effect.The results implied that when the thickness of the disk magnet is relatively thin,the specific negative magnetocrystalline anisotropy will make the vortex disappear or form an unstable double core vortex structure.While in the case of larger thickness,the negative magnetocrystalline anisotropy can inhibit the formation of magnetic vortices on the side,making the magnetic vortices more stable in the disk plane.However,the excessively intensive magnetocrystalline anisotropy will cause the vortex core to break in the center,forming a separated vortex state.Although the chirality of the upper and lower parts of the vortex is opposite,the polarity of the vortex core remains constant,and remanent magnetization exists in the zero field.Therefore,the negative magnetocrystalline anisotropy makes it possible for the stable formation of magnetic vortices at higher thickness,which also provides ideas for the study of magnetic vortices.