Study On The Magnetoelastic Anisotropy Of Fe,Co And Ni Magnetic Films

Magnetic anisotropy,as the most basic and important physical property of magnetic materials,plays a very important role in the application of our daily life.However,with the gradual commercial application of flexible wearable electronic devices,the research on flexible magnetic electronic devices has continued to grow and develop,and has attracted more and more attention for researchers.In the process of flexibility about magnetic materials,an important physical effect is magnetoelastic anisotropy.At present,many researchers have studied the magnetic properties of magnetic thin films grown on flexible mica and polyethylene terephthalate（PET）substrates by mechanically bending substrates.While there is little relevant experimental research about magnetoelastic anisotropy of the classical Fe,Co and Ni magnetic elements which are widely used.Therefore,in response to the above problems,we have designed a method for accurately controlling the magnetic anisotropy of Fe,Co and Ni magnetic thin films by applying stress/strain in situ and studied the magnetoelastic anisotropy of Fe,Co and Ni magnetic films in both qualitative and quantitative aspects.The main research contents are as follows:1.Magnetic films of Fe,Co and Ni are deposited on a polyvinylidene fluoride（PVDF）substrate with anisotropic thermal expansion by magnetron sputtering,and a uniaxial compressive stress can be generated during the temperature reduction of the PVDF substrate and transferred to the magnetic films.So,the effect of stress/strain on its magnetic properties was investigated.By testing the variation of the normalized hysteresis loop under different stresses,the experimental results show that Co has a"positive"magnetoelastic anisotropy（the easy magnetization axis is perpendicular to the direction of stress/strain application）,while Fe and Ni have"negative"magnetoelastic anisotropy（the easy magnetization axis is parallel to the direction of stress/strain application）.With the increase of stress,the easy magnetization axis of Fe,Co and Ni magnetic films is more and more easy,the remanence ratio is getting larger and larger,and the coercive field is getting larger and larger;But the hard magnetization axis is more and more difficult,the remanence ratio is getting smaller and smaller,and the coercive filed remains unchanged.2.Based on the above experimental ideas and methods,the relationship between magnetic torque and magnetic anisotropy constant is obtained by testing the anisotropic magnetoresistance（AMR）.The magnetic anisotropy constants of Fe,Co and Ni magnetic films under different stress/strain environments were obtained by nonlinear curve fitting of AMR curves.Further,by linear fitting of the magnetic anisotropy constants under different stress/strain,the stress-coefficient of magnetoelastic anisotropy about Fe,Co and Ni magnetic films were quantitatively computed to be（6.31±0.19）×10³ erg cm^-33 GPa^-1、（2.71±0.13）×10⁴ erg cm^-33 GPa^-11 and（2.46±0.19）×10⁵ erg cm^-33 GPa^-1,respectively.The gradual increase of the stress-coefficient about Fe,Co and Ni magnetic films indicates that the stress is more and more easy to regulate the magnetic properties.This significant test result can also be consistently verified from the hysteresis loop determined by the stress.In conclusion,the magnetoelastic anisotropy of Fe,Co and Ni magnetic films is qualitatively and quantitatively analyzed,which broadens our research ideas and methods of magnetoelastic anisotropy about magnetic materials and contributes us to design different kinds of flexible magnetoelectronic devices by utilizing their different physical properties.