Enhancing next-gen electronics with cobalt-tin-sulfur compounds

Researchers from Tohoku University have made a breakthrough which has the potential to enhance next-generation electronics by enabling non-volatility, large-scale integration, low power consumption and high speed in spintronic devices. These devices, represented by magnetic random access memory (MRAM), utilise the magnetisation direction of ferromagnetic materials for information storage and rely on spin current, a flow of spin angular momentum, for reading and writing data. Conventional semiconductor electronics have faced limitations in achieving these qualities.

However, the emergence of three-terminal spintronic devices, which use separate current paths for writing and reading information, presents a solution with reduced writing errors and faster writing speed. However, reducing energy consumption during information writing, specifically magnetisation switching, remains a concern.

A new method for mitigating energy consumption during information writing is the utilisation of the spin Hall effect, where spin angular momentum (spin current) flows transversely to the electric current. However, it is difficult to identify materials that exhibit a significant spin Hall effect, due to the lack of clear guidelines.

Yong-Chang Lau and Takeshi Seki, co-authors of the study, investigated a compound known as cobalt-tin-sulfur (Co3Sn2S2), which exhibits ferromagnetic properties at temperatures below 177 Kelvin (-96°C) and paramagnetic behaviour at room temperature. “Notably, Co3Sn2S2 is classified as a topological material and exhibits a remarkable anomalous Hall effect when it transitions to a ferromagnetic state due to its distinctive electronic structure,” Lau and Seki said.

The researchers used theoretical calculations to explore the electronic states of ferromagnetic and paramagnetic Co3Sn2S2, revealing that electron-doping enhances the spin Hall effect. The researchers used thin films of Co3Sn2S2 partially substituted with nickel (Ni) and indium (In) that were synthesised. The experiments found that Co3Sn2S2 exhibited the most significant anomalous Hall effect, while (Co2Ni)Sn2S2 displayed the most substantial spin Hall effect. There was an intricate correlation between the Hall effects, which provided a clear path to discovering new spin Hall materials by leveraging existing literature as a guide.

“This will hopefully accelerate the development of ultralow-power-consumption spintronic devices, marking a pivotal step toward the future of electronics,” Seki said.

The research findings were published in the journal Physical Review B.

Top image caption: A schematic image of conversion phenomenon from charge current to spin current based on spin Hall effect in Co3Sn2S2 layer. Image credit: Takeshi Seki et al.