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

• Published in: Scientific reports Vol. 11; no. 1; p. 21448
• Main Authors: Nozaki, Tomohiro, Tamaru, Shingo, Konoto, Makoto, Nozaki, Takayuki, Kubota, Hitoshi, Fukushima, Akio, Yuasa, Shinji
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 02.11.2021; Nature Publishing Group UK
• Subjects: Anisotropy; Dielectric constant; Heavy metals; Information processing; Interfaces; Oxidation; Voltage
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-00960-w

Abstract 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 TiO x 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 TiO x 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.