Preparation,Magnetic Properties And Giant Magnetostriction Effect Of The Nano-Multilayer Films

The magnetostriction effect can be described most generally as the deformation of a body in response to a change in an external magnetic field.The discovery of giant magnetostriction(GMS) and the progress in this field have demonstrated its important value in applications.The Terfenol-D GMS thin films have high electronic resistivity,high magnetic permeability,low magnetic hysteresis,and weak magnetocrystalline anisotropy.The GMS films with low field sensitivity are useful to the new type electro-mechanical transformation system.In this work,we developed a simple way to prepare [Th/Fe/Dy]_n nano-multilayer film with precise composition of Tb_0.27Dy_0.73Fe₂ and insert soft layer[SL/Tb/Fe/Dy]_n nano-multilayer film with low field GMS sensitivity. Meanwhile,the structure,magnetic properties and giant magnetostriction of the nano-multilayer films are studied.And the main contents and results are as follows:1.Pure element targets Tb,Dy and Fe were used to deposit with precise composition[Th/Fe/Dy]_n nano-multilayer films.(1) The compositions of[Tb(2nm)/Fe(4nm)/Dy(3nm)]_n nano-multilayer film was analyzed by energy dispersive analysis system of X-ray(EDX) and inductively coupled plasma atomic emission spectroscopy(ICP-AES).The analyzed composition of nano-multilayer film was(Tb_0.27Dy_0.73) Fe₂.(2) SEM measurement shows that the morphology and microstructure of those two as deposited nano-multilayer films have columnar structures consisting of grains oriented perpendicularly to the film plane.(3) The[Tb/Fe/Dy]_n nano-multilayer films were deposited at room temperature.a.The as deposited nano-multilayer film and nano-multilayer films annealed at temperature 300℃are still in amorphous state.At the annealing temperature of 400℃,the R-Fe₂ grains begin to be segregated from the amorphous matrix. b.The M(o｜¨)ssbauer spectrum and the magnetic hysteresis loops show that the magnetic moments distributed orientation of nano-multilayer films are changed by the annealing temperature.In as deposited state and annealed temperature of 400℃,magnetic moments distributed orientation of nano-multilayer films is perpendicular to the film plane;yet at annealing temperature of 300℃,500℃and 600℃,magnetic moments distributed orientation of nano-multilayer films is in random.c.Because nano-multilayer films(in as deposited state and annealing temperature at 400℃) have perpendicular anisotropy,i.e.,the magnetic domains distributed orientation is perpendicular to the film plane.When the external field is parallel to the film plane,the magnetic field can not magnetize the magnetic moments freely,so the GMS increases almost linearly in the applied field.When the magnetic domains distributed orientation of nano-multilayer films(annealed temperature of 300℃,500℃and 600℃) is in random,the GMS of these nano-multilayer films increases rapidly at first and then almost saturates at the external filed of 0.32T.(4) The[Tb/Fe/Dy]_n nano-multilayer films were deposited at 300℃substrate temperature.a.The R-Fe₂ nano-grains begin to be segregated from the amorphous matrix in as deposited nano-multilayer film.b.When the annealed temperature lower than 400℃,the magnetic domains distributed orientation is perpendicular to the film plane;when the annealed temperature higher than 500℃,the magnetic domains distributed orientation is parallel to the film plane.c.The GMS of the nano-multilayer films is also determined by the magnetic moments distributed orientation.(5) The GMS value in nano-multilayer films deposited at 300℃substrate temperature was higher than those nano-multilayer films deposited at room temperature. (6) The huge influence of the magnetic anisotropy on the field dependence of the magnetostriction is considered by different types of magnetization processes.2.The insert soft layer[SL/Tb/Fe/Dy]_n nano-multilayer films combine the giant magnetostrictive materials([Tb/Fe/Dy]_n) and materials with large magnetic polarizations(Fe and FINEMET).(1) Because of the interaction between the soft layer and the GMS layer,the [SL/Tb/Fe/Dy]_n nano-multilayer film has low saturation magnetization, high GMS performance and lower coercivity,and the magnetic domains distributed orientation is parallel to the film plane.(2) The[Fe/Tb/Fe/Dy]_n nano-multilayer films in as deposited state and annealed at temperature 300℃are still in amorphous state.At the annealing temperature of 400℃,theα-Fe and R-Fe₂ grains begin to be segregated from the amorphous matrix.Because of the interaction between the soft layer Fe and the GMS layer,the magnetic moments distributed orientation of all[Fe/Tb/Fe/Dy]n nano-multilayer films are paralleled to the film plane;and all[Fe/Tb/Fe/Dy]_n nano-multilayer films have lower coercive force,higher saturated magnetic magnetization intensity and better low field GMS performance.(3) Because the soft magnetic properties of FINEMET layer are much than those of Fe layer,the GMS performance of[FINEMET/Tb/Fe/Dy]_n nano-multilayer films are higher than that of[Fe/Tb/Fe/Dy]_n nano-multilayer films.(4) The[Fe/Tb/Fe/Dy]_n nano-multilayer films were deposited at 300℃substrate temperature.Theα-Fe and R-Fe₂ grains begin to be segregated from the amorphous matrix at the as deposited nano-multilayer film.The magnetic hysteresis loops show that the coercive force decreases and the saturated magnetization intensity increases by increasing annealing temperature.