| Perpendicular magnetic anisotropy(PMA)materials have received considerable interest in recent years owing to their potential excellent properties in the next generation of high-density storage devices,such as high thermal stability factor and low critical current density for magnetization reversal.Ferromagnetic(FM)/non-magnetic heavy metal(HM)multilayers structure film materials and ferromagnetic(FM)/oxide heterostructure film are the most commonly studied two types of PMA materials at present.They exhibit excellent performance in magnetic tunnel junctions with PMA.Studies suggested that the PMA of HM/FM multilayer structure films and that of FM/oxide multilayer structure films stem from the interfacial interaction.Therefore,PMA is enhanced by increasing interfacial interaction in this paper.In this paper,the Co-based Heusler alloy Co Mn Si with large spin polarization was selected as the ferromagnetic layer,the precious metal Pd as the heavy metal layer,and the antiferromagnetic oxide Ni O as the oxide layer.The PMA of Pd/Co50Mn25Si25(CMS*)/Pd multilayers structure films and that of Pd/Co55Mn25Si20(CMS)/Ni O/Pd multilayer structure films were investigated respectively.The specific experimental contents are as follows:1.By inserting a heavy metal(Pd)layer and inserting an N-layer FM/HM layer to increase the interface effect of the film,thereby increasing the perpendicular magnetic anisotropy of the film.Under the same experimental conditions,the sample group Pd/CMS*/Pd,the sample group Pd/CMS*1/Pd/CMS*2/Pd inserted into Pd layer and the sample group Pd/CMS*1/[Pd/CMS*2]N/Pd inserted into[Pd/CMS*2]Nlayers were respectively prepared by magnetron sputtering.The magnetization hysteresis loops of the sample films were measured by an alternating gradient magnetometer and the experimental results were compared and analyzed.The experimental results show that after the insertion of 0.8 nm Pd layer into the Pd/Co50Mn25Si25/Pd structure,the range of the thickness of CMS*with PMA increases from 4 nm-7 nm to 4 nm-9 nm,and the controllable range of the thickness is increased by 66.67%,and the overall PMA of the film is significantly enhanced.After[Pd/CMS*2]Nmultilayer is inserted into the Pd/Co50Mn25Si25/Pd structure,the PMA of the film is the strongest when N=1,and the thickness of CMS*with PMA increases to 10.5 nm.As the number of[Pd/CMS*2]Nlayers increases,the rectangularity of the out-of-plane hysteresis loop decreases,and there is a negative linear correlation with the number of layers.2.By increasing the content of Co(Co55Mn25Si20),the lattice mismatch between the ferromagnetic layer and the oxide layer is improved,and the perpendicular magnetic anisotropy of the film is enhanced.The Pd/Co55Mn25Si20(CMS)/Ni O/Pd films with heavy metal/ferromagnetic interface,ferromagnetic/oxide interface and ferromagnetic/antiferromagnetic interface were constructed by introducing anti-ferromagnetic oxide(Ni O)to increase the interfacial interaction and enhance the perpendicular magnetic anisotropy of the films.The structures of Pd,Co55Mn25Si20,Co50Mn25Si25and Ni O were characterized by XRD,and the PMA of Pd/Co55Mn25Si20(CMS)/Ni O/Pd multilayers and that of Pd/Co50Mn25Si25(CMS*)/Ni O/Pd multilayers were compared and analyzed.The maximum effective PMA energy,obtained from the Pd(6 nm)/Co55Mn25Si20(5.5 nm)/Ni O(1.0 nm)/Pd(6 nm)multilayer film which is sputter-deposited on glass at a substrate temperature of 350°C,is 0.695 Merg/cm3.By appropriately increasing the Co content,a wider FM layer thickness range(3–8 nm)that achieved PMA was obtained.The oxide in the traditional FM/oxide structure was replaced by the antiferromagnetic Ni O to obtain a wider oxide layer thickness of 0.4–7.6 nm,or even wider. |
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