Interface Effect On Vertical Magnetic Anisotropy And Electrical Transport Properties Of CoHF Multilayers

In recent years,the popularization of 5G has made people take a new step on the road of informatization.In the complex information network,the rapid and stable access to information has become the key to the development of information industry.In order to improve the storage density and storage stability,researchers turn to magnetic storage technology.Storage media with perpendicular magnetic anisotropy(PMA)is helpful to increase storage density and storage stability since the ultra-paramagnetic effect is avoided when the record size decreases.Therefore,it is one of the cores of magnetic storage technology to realize PMA characteristics with strong and wide adjustable range in magnetic recording medium.At present,Co/precious metal system and CoFeB system have been studied and mature,but the adjustable range of realizing PMA characteristics is relatively narrow.In order to solve the above problems,the CoHf binary alloy was selected as the ferromagnetic layer in this study.The heavy metal Hf was used to improve the spin-orbit coupling energy of the material,thus further promoting the generation of PMA.In this study,CoHf was used as a ferromagnetic layer to prepare three series of films with cyclic structure,sandwich structure and composite cyclic structure on Si(SiO2)substrate.The Perpendicular magnetic anisotropy and Anomalous Hall effect(AHE)of three different types of CoHf multilayer films are discussed.In the[CoHF/Pd]3 structure,Ta/[CoHf(1.0 nm)/Pd]3/Pd annealed at 350? has the strongest PMA with Mr/Ms=0.96,effective magnetic anisotropy Keff=4.31×106 erg/cm3 and coercivity H,=366.5 Oe.In addition,the[CoHf/Pd]3 structure has a stronger PMA and greater adjustability than that of the[Co/Pd]3 multilayer films.In the Pd/CoHf/MgO sandwich structure,the saturation magnetization of the thin film decreases.The Ta/Pd/CoHf(3.5 nm)/MgO/Pd film annealed at 350? has the optimal structure with the strongest PMA characteristics.Its rectangularity is 0.93,effective magnetic anisotropy Keff value is 8.67×105 erg/cm3 and coercivity is 645.5 Oe.TEM analysis showed that hard magnetic phase of Co7Hf was formed in the thin film.The results of the transport test show thatin addition to the normal Hall effect,there is a strong topological Hall effect contribution when the measured temperature isbelow 200 K.The contribution of the topological Hall effect decreases with lowing temperature,and increases with the CoHf thickness increasing.In the[Pd/CoHf/MgO]3 circulating film,with Pd/CoHf/MgO as the circulating layer,the Ta(4 nm)/[Pd(1.7 nm)/CoHf(3.0 nm)/MgO(1.5 nm)]3/Pd(1.7 nm)annealed at 350? has the strongest PMA characteristics.Its rectangularity is 0.93,effective magnetic anisotropy Keff value is 3.89×105 erg/cm3 and coercivity is 480.6 Oe.Even more significantly,the topological Hall effect can be realized at room temperature as the thickness of the CoHf layer increases to 3.0 nm.The sample with tCoHf=3.5 nm obtains the strongest topological Hall effect at room temperature.In this study,the perpendicular magnetic anisotropy and Hall effect of three different structures in CoHf multilayer films were regulated,which provided a new material system for the development of magnetic storage,and could help to the research and development of spin devices.