The Study On Preparation And Characterization Methods Of CoFe-based Magnetic Thin Films

In this study,magnetic thin films of CoFeB and TbFeCo were prepared.The preparation process of these thin films was optimized.Finally,the magnetic properties,Magneto-optical Kerr effect,anomalous Hall effects and structural properties of the films were analyzed.The main contents are as follows:Firstly,we prepared the structure of Ta/CoFeB/MgO/Ta films were prepared by magnetron sputtering system,and we systematically studied the magnetic properties and structural properties of CoFeB films.CoFeB films were prepared by different sputtering powers and annealed in a vacuum chamber.We found that the magnetic properties of the films sputtered at lower power are always isotropic before and after annealing.In contrast,the magnetic properties of the films sputtered at higher power changes from uniaxial anisotropy to isotropy.X-ray diffraction analysis reveals that the structure of thin films changes from amorphous state to nanocrystalline after annealing.When the annealing temperature is over 400 ℃,the intensity of the(110)peak in the CoFeB film sputtered at lower power is higher than that deposited at higher power.For the CoFeB film sputtered at lower power the grain size obtained from Scherrer formula increases faster than that at high power.This is consistent with the finding that coercivity of the film sputtered at lower power is larger than that deposited at higher power after annealing over 400 ℃.Then,we studied of the thickness of the magnetic layer of CoFeB films.It’s found that with the increase of the thickness of the magnetic films,the in-plane magnetic anisotropy is changed from weak to strong and then weak,and when the thickness of the magnetic layer is 36 nm,the in-plane magnetic anisotropy of the films is the largest.Secondly,we prepared the structure of Ta/Pd/CoFeB/MgO/Ta films,and explored it’s perpendicular magnetic properties systematically.We investigated that annealing time,thickness of magnetic layer and MgO layer make much importance to the perpendicular magnetic properties of CoFeB films.When we studied the effect of annealing time on the anomalous Hall effects of CoFeB thin films,we found that if the thickness of the magnetic layer was 1.6 nm,MgO layer was about 1.8 nm,while the film was annealed at a temperature of 30 min,the films got the best vertical magnetic anisotropy.It was observed that the CoFeB films had excellent perpendicular magnetic anisotropy in a certain thickness range,and the CoFeB had a maximum coercivity when the CoFeB layer thickness was 1.6 nm.In the study of the effect of MgO layer thickness on the anomalous Hall effects of CoFeB films(increased from 0.6 nm to 3 nm).It is found that the coercivity increase first and then decrease with the increase of MgO thickness.Then,we prepared the structure of Ta/TbFeCo/Ta films by using a Tb-FeCo mosaic target,and studied the magnetic and structural properties of TbFeCo thin films systematically.It was found that the as-deposited film is amorphous,and we could change the sputtering power to make the TbFeCo films show two different states of rich RE and TM.When we studied the influence of the thickness of the magnetic layer on the magneto-electric and magneto-optical effects of TbFeCo thin films,we found that the coercivity of rich-FeCo films increases with the increase of film thickness.At the same time,we also verify that the anomalous Hall voltage is inversely proportional to the film thickness.Finally,according to the experimental results,we prepared the structure of Ta/Pd/CoFeB/MgO/TbFeCo/TbFeCo/Ta/Si(substrate)films.We found that the CoFeB layer and the TbFeCo layer were reversed under different external magnetic fields respectively.