Large voltage-induced coercivity change in Pt/Co/CoO/amorphous TiOx structure and heavy metal insertion effect

There is urgent need for spintronics materials exhibiting a large voltage modulation effect to fulfill the great demand for high-speed, low-power-consumption information processing systems. Fcc-Co (111)-based systems are a promising option for research on the voltage effect, on account of their large perpendicular magnetic anisotropy (PMA) and high degree of freedom in structure. Aiming to observe a large voltage effect in a fcc-Co (111)-based system at room temperature, we investigated the voltage-induced coercivity (H-c) change of perpendicularly magnetized Pt/heavy metal/Co/CoO/amorphous TiOx structures. The thin CoO layer in the structure was the result of the surface oxidation of Co. We observed a large voltage-induced H-c change of 20.2 mT by applying 2 V (0.32 V/nm) to a sample without heavy metal insertion, and an H-c change of 15.4 mT by applying 1.8 V (0.29 V/nm) to an Ir-inserted sample. The relative thick Co thickness, Co surface oxidation, and large dielectric constant of TiOx layer could be related to the large voltage-induced H-c change. Furthermore, we demonstrated the separate adjustment of H-c and a voltage-induced H-c change by utilizing both upper and lower interfaces of Co.

Automated summary

This study identified a large voltage-induced coercivity (H-c) change in a fcc-Co (111)-based system, which may be related to the properties of Co thickness, surface oxidation, and TiOx layer.