Interfacial State-modulated Properties In Anomalous Hall Effect Materials

Spintronics is a new interdiscipline that studies electron spin related transport processes and corresponding devices. Spintronic devices based on the charge and spin properties of electrons are widely used in quantum computers, nano-logic devices, magnetic storage, Satellite, personal computers and other advanced areas. Compared with the traditional electronic devices, the novel spintronic devices have the advantages of non-volatility, high integration, fast processing speed and low energy consumption, and are better able to meet the demand of the miniaturization, integration and intelligence of the future electronic devices. Therefore, it is very important to design spin-electronic materials with high performance. However, there are some problems in the application of spintronic materials at present. ?1? The magnetic thin film material as the memory device should have good perpendicular magnetic anisotropy; ?2? The output signal should be large; ?3? At the same time, to meet the follow-up semiconductor technology, the material needs to go through 350 ? annealing process, it should have good thermal stability. The following research work around these three issues. Since the previous researchers mainly focus on the aspect of atomic scale and geometry, such as film thickness and interface matching degree, stress, defects, roughness, diffusion. Acturely, the impact of micro-interfacial state of is more important. The following researches have been carried out:?1? The high oxygen storage/release capability of the catalyst Ru is used to manipulate the interfacial electronic structure in MgO/CoFeB/Ta/MgO films to obtain perpendicular magnetic anisotropy ?PMA?. Insertion of an ultrathin Ru layer between the CoFeB and Ta layers in MgO/CoFeB/Ta/MgO films effectively induces PMA without annealing. Ru plays a catalytic role in Fe-O-Ta bonding and isolation at the metal-oxide interface to achieve moderate interface oxidation. This work would provide a new approach toward catalyst-induced PMA for future CoFeB-based spintronic device applications.?2? The role of the spin-dependent interface scattering on the anomalous Hall effect ?AHE? of MgO/CoFeB/Ta/MgO film was been well studied. The anomalous Hall resistivity value can be significantly enhanced for inserting an ultrathin Mg layer between the CoFeB and Ta layers, due to the improved diffuse scattering of impurity scattering centers at the interfaces. This work is of great importance for improving the properties of the magnetized spintronic devices based on AHE through artificial interfacial modification.?3? Chemical reactions at the ferromagnet/oxide interface in [Pt/Fe]₃/MgO and [Pt/Fe]₃/SiO₂ multilayers before and after annealing were investigated by X-ray photoelectron spectroscopy. The results show that Fe atoms at the Fe/MgO interface were completely oxidized in the as-grown state and significantly deoxidized after vacuum annealing. However, only some of the Fe atoms at the Fe/SiO₂ interface were oxidized and rarely deoxidized after annealing. The anomalous Hall effect was modified by this interfacial chemical reaction. The saturation anomalous Hall resistance was greatly increased in the [Pt/Fe]₃/MgO multilayers after annealing and was 350% higher than that in the as-deposited film, while Rxy of the [Pt/Fe]₃/SiO₂ multilayer only increased 10% after annealing.?4? The perpendicular magnetic anisotropy ?PMA? and the anomalous Hall effect ?AHE? in Co/Ni multilayer were optimized by manipulating its interface structure ?inducing HfO₂ capping layer and Pt insertion? and post-annealing treatment. A strong PMA can be obtained in Co/Ni multilayers with HfO₂ capping layer even after annealing at 400 ?. The heavy metal Hf may improve the interfacial spin-orbit coupling, which responsible for the enhanced PMA and high annealing stability. Moreover, the multilayer containing HfO₂ capping layer also exhibited high saturation anomalous Hall resistivity through post-annealing, which is 0.85 ?? cm after annealing at 375 ?,211% larger than in the sample at deposited state which is only 0.27 ?? cm. The enhancement of AHE is mainly attributed to the interface scattering through post-annealing treatment.