Study On The Microstructure And Magnetic Properties Of Fe₈₁Ga₁₉ Thin Films

As a new type of functional material,Fe-Ga alloy thin film is expected to overcome the shortcomings of bulk Fe-Ga alloy and has better performance than Terfenol-D thin film.Therefore,the study on Fe-Ga thin film is the frontier field of condensed matter physics and material science.In this paper,different thicknesses of Fe81Ga19 thin film were deposited on MgO(100),MgO(110),MgO(111),Si(100)and SrTiO3(100)substrates by RF magnetron sputtering technique.In order to investigate the effects of thicknesses,substrates orientation and substrates types on the structure and magnetic properties of Fe81Ga19 thin films,the surface morphology,crystal structure and magnetic properties of Fe81Ga19 thin films were characterized by atomic force microscopy(AFM),X-ray diffractometer(XRD)and vibrating sample magnetometer(VSM).The results of surface morphology and crystal structure show that the particle size of Fe81Ga19 film increases gradually,from 60 nm to 106 nm,the surface is more and more smooth and the compactness is getting better and better with the increase of thicknesses.The films on different substrate orientations and different substrates have the same size and shape.In contrast,Fe81Ga19/MgO(100)films have higher density and higher substrate coverage.All of the Fe81Ga19 thin films have a body-centered cubic structure and the main phase is a disordered A2 phase.With the increase of thicknesses,the grain size of the film increases,from 13 nm to 66 nm,and the crystallinity of the film becomes better.Therefore,increasing the thicknesses is beneficial to the crystallization of Fe81Ga19 film.In the prepared samples,the crystal structure of Fe8iGai9/MgO(100)thin films is better than others.In addition,the film was heated to 500 ℃ in N2 atmosphere using a tube furnace,and it was found that the particle size of the film was further increased but the effect on the crystal phase was insignificant.The results of magnetic measurements show that all Fe81Ga19 thin samples have typical ferromagnetic properties.Among of them,the magnetic properties of the sample(thickness is 50 nm)are better and its magnetic properties are as follows:the coercivity is about 27 Oe,the saturation magnetization is 10073 Oe,the saturation magnetic field is about 50 Oe and the remanence ratio of 0.98.With the increase of thicknesses,the coercivity of the film samples increases first and then tends to remain unchanged,the saturation magnetization decreases first and then increases,and the residual magnetization decreases.In contrast,the Fe81Ga19 thin films deposited on the MgO(100)substrate have better magnetic properties.And the heat treatment has a greater impact on the magnetic properties of the film,resulting in significant decrease of saturation magnetization and residual magnetization,and increase of coercivity.In summary,Fe81Ga19/MgO(100)films with thickness of 300 nm and 50 nm show good crystallinity,compact structure,small coercive force,large saturation magnetization and small saturation magnetic field.