Preparation And Stress Dependence Study Of Tetragonal Distorted FeCo Thin Films For Magnetic Recording Media

With the coming of the era of artificial intelligence and big data,people are more and more urgent to collect,store and process information efficiently.High density storage needs the support of new technology,new theory and new materials.The development of new technology mainly includes PMR,SMR and MAMR.The development of new theory mainly includes the discovery of magnetoresistance(MR)effect and giant magnetoresistance(GMR)effect.With the development of new materials,superparamagnetic limit is the main problem.At present,the recording potential of L10 phase FePt materials has reached the extreme.In order to further reduce the volume of recording bits and achieve higher density storage,it is necessary to explore and prepare new materials with higher magnetocrystalline anisotropy and saturation magnetization.Therefore,bct-FeCo materials have become a research hotspot.In this thesis,the influence of thermal stress and external stress on the magnetic properties of bct-FeCo films and the structure of[FeCo/Rh]n multilayers were studied.In the first part,CrRu(002)/Rh(002)/FeCo(002)/Rh multilayered films were deposited on glass and NaCl substrates by magnetron sputtering.The effects of thermal stress on the magnetic properties of bct-FeCo films were studied.1.When the sputtering parameter of CrRu film is 5 mTorr Ar,substrate temperature is 300℃,DC sputtering power is 120 W,the better CrRu(002)texture can be obtained;when the thickness of CrRu layer is 20 nm,the single Rh(002)orientation can be obtained;and(002)oriented FeCo film can be epitaxial grown on the Rh layer.2.FeCo films with the same thickness were deposited on glass substrate,and the magnetic crystalline anisotropy of Fe40Co60 films was higher than that of Fe50Co50 films.3.When the thickness of FeCo thin film is more than 2 nm,the Ku value of FeCo thin film on glass and NaCl substrate begins to decrease;when FeCo thin film is the same,the magnetocrystalline anisotropy energy of FeCo thin film on NaCl substrate is higher than that on glass substrate,which is due to the effect of thermal stress.4.Through the analysis of TEM and in plane XRD,it is found that crystal lattice distortion occurs in CrRu and Rh layers under the action of thermal stress.Similarly,it is known that the lattice distortion also occurs in FeCo films.In the second part,the magnetic properties of[FeCo/Rh]n multilayers were studied by the preparation of their structures.1.When the thickness of FeCo layer is 4～10 ML,the saturation magnetization value is lower than the theoretical value,which is due to the superparamagnetic phenomenon of nanocrystalline particles with a certain size formed by the thin film.When the thickness is 12 ML,the saturation magnetization is close to the theoretical value of 1500 emu/cc.2.When the thickness of Fe40Co60 layer is 12 ML,the magnetocrystalline anisotropy can be improved by adjusting the thickness of Rh layer.The experimental results show that the values are about 9.5×107 erg/cc.In the third part,a special substrate frame was designed to bend the flexible substrate,and then CrRu(20 nm)/Rh(20 nm)/Fe40Co60(2 nm)/Rh(2 nm)multilayer structure was deposited.After sputtering,the external force was released,so that the film was subjected to an in-plane shrinkage external stress.The effect of external stress on the magnetic properties of bct-FeCo film was studied to get the following conclusion:1.The saturation magnetization values of Fe40Co60 films deposited on glass and Kapton 500HN substrates are about 1500 emu/cc.2.Compared with glass substrate,the magnetocrystalline anisotropy of Fe40Co60 film deposited on flexible substrate is improved,and the value is 1.47×107 erg/cc.In conclusion,thermal stress and external stress have certain effect on improving the magnetocrystalline anisotropy of bct-FeCo thin films,while the formation of[FeCo/Rh]n multilayer structure by alternate sputtering is weak for improving the magnetocrystalline anisotropy.