| In recent years,as new-generation information technologies such as artificial intelligence,the Internet of Things,and big data have become key foundations and important engines for promoting socio-economic development,the demand for an advanced information storage technologies keeps growing.The spin-torque magnetic random access memory?STT-MRAM?based on perpendicular magnetic anisotropy?PMA?material,with the advantages of higher magnetic storage density,good thermal stability,etc.,is attracting more and more research attention to the magnetic multilayer film with PMA.Subjecting Co-based multilayer nano-films to scrutiny,through a variety of control methods,this research systematically studies and analyzes the magnetic anisotropy and magnetization reversal process of magnetic multilayer films,mainly consisting of the following components:1.The effects of different deposition cycles,Ta layer thickness and annealing temperatures on the magnetic anisotropy of the[Ta/CoFe]n multilayer film,the microstructure of the films,and the high-frequency magnetic properties were studied,and the SAF with the CoFe/Cu/CoFe structure was used to systematically control the magnetoresistance of spin valves and the exchange field.The results show that the high-frequency performance of the film has a strong response to the number of cycles,the thickness of the Ta layer,and the annealing temperature.It is also found that the SAF structure can significantly increase the exchange field of the spin valve film,while the magnetoresistance of the spin valve depends more on the annealing temperature.2.The effects of the repeat numbers,the Co layer thickness,the patterned film,and the low temperature on the perpendicular magnetic anisotropy?PMA?and reversal field distribution of the[Pt/Co]N multilayer film were studied.It is found that the PMA of the sample with the increase of the repeat number,but decrease with the rising Co layer thickness.Both control methods make the nucleation field of magnetic domains move toward+Hr and the annihilation field move toward-Hr,lengthening the reversible reversal process and decreasing the proportion of irreversible reversal.In addition,compared with continuous films,the coercivity and remanence ratios of[Co/Pt]N multilayer film line arrays and dot arrays become larger,the positions of nucleation and annihilation fields are getting closer and closer,and the range of reversible flipping becomes narrower.Moreover,different pattern structures have different effects on the reversal field distribution.As the external temperature decreases,the coercivity Hc and saturation magnetization Ms of the sample become larger.It is also found that[Pt/Co]N multilayer films exhibit stronger perpendicular magnetic anisotropy at low temperature.3.The effects of CoFe thickness,sample structure,and magneto-annealing conditions on the vertical magnetic anisotropy,magnetic domain structure,and magnetization inversion process of[Pt/CoFe/MgO]n multilayer films were studied.It is found that the PMA and irreversible reversal field distribution of the sample strongly depend on the thickness of CoFe,and the magnetic domain width in the film changes significantly when the sample structure is inverted;annealing by a certain degree can effectively improve the PMA of the sample.Moreover,the PMA of[Pt/CoFe/MgO]10thin film has a stronger response to low temperature than the[Co/Pt]n multilayer film.4.The effects of kinds,thickness and sputtering power of heavy metal layer on the PMA of CoFe multilayer films were studied.The results show that the strength of the[Pt/CoFe/X]100 perpendicular magnetic anisotropy depends on the 5d electron number of the heavy metal layer:the smaller the 5d electron number of the cover material,the longer the reversible reversal process of the films.It is also discovered that by adjusting the thickness of the heavy metal layer and the sputtering power,the PMA and reversal field distribution of the sample can be effectively regulated. |
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