Prof. Pu Yu’s research group achieved a novel pathway to achieve electric field control of magnetism through ionic evolution
On 18th December 2017, a research team led by Prof. Pu Yu (Department of Physics, Tsinghua University) published their research results entitled “Electric field control of ferromagnetism through oxygen ionic gating” in the journal of Nature Communications. In this work, using a simple resistive switch device architecture of Co/SrCoO2.5 heterostructure, the team has demonstrated an effective pathway to control the ferromagnetism in Co metal through electric field controlled oxygen ion evolution within an oxide SrCoO2.5 layer.
Electric-field control of magnetism, i.e. magneto-electric coupling, forms one of the key approaches to achieve next generation high-speed and low-power spintronic. Recently, researchers have proposed that oxygen ions in oxide materials can be utilized to effectively manipulate the magnetic properties of ferromagnetic metal layers in metal/oxide hetero-structures, through electric-field controlled reversible redox reactions within metal layers. However, to facilitate the oxygen ion migration and necessary redox reactions, extended operating times (several seconds or even minutes) and elevated temperature conditions (~100 °C) are typically required. Thus, achieving high-speed performance at room temperature remains one of the main challenges before such simple architectures can be readily adopted in modern semiconductor technologies.
Among the complex oxides, the brownmillerite SrCoO2.5 (SCO) possesses a unique oxygen-vacancy ordered crystalline structure, providing a suitable condition for the ionic transport. Early this year, based on this material, Prof. Yu’s group has demonstrated an electric field controlled tri-state phase transformation with dual ion evolution. Inspired by the previous work, the SCO was employed in the current study as a potential fast ionic gate to realize magneto-electric coupling in metal/insulator (Co/SCO) junctions. The group has discovered that the simple device exhibits nice resistance switching behavior, i.e. the resistance can be switched between different states under an external electric field. Interestingly, they have revealed that the magnetic property of the Co layer is strongly correlated with the resistant state, thus showing the magneto-electric coupling nicely. They further proved that both behaviors are dominated by the ionic transfer at the interface, in which the variation of interfacial oxygen ion concentration modulates strongly both the interface resistive state and the magnetic anisotropy of the Co layer. Due to the rapid ion transportation at the interface and its independence to the bulk redox, the room-temperature device response speed is about four orders of magnitude faster than previous Co/GdOx systems, which could be further improved through device optimization.
The current study provides a solid foundation to combine the study of magneto-electric coupling and resistance switch effects together, with potential for creating multi-functional devices compatible with modern semiconductor technologies.
Prof. Pu Yu is the corresponding author of the paper, and Dr. Hao-Bo Li is the first author. The work was done with the close collaboration of a large group of people, which include Prof. Cewen Nan’s group at the School of Materials Science and Engineering, Tsinghua University, Prof. Lin Gu’s group and Prof. Kui Jin’s group at Institute of Physics, Chinese Academy of Science and Prof. Hui Liu’s group from Nankai University. The project was financially supported by National Basic Research Program of China, National Natural Science Foundation of China, The Initiative Research Projects of Tsinghua University, Strategic Priority Research Program of Chinese Academy of Sciences, and the Beijing Advanced Innovation Center for Future Chip (ICFC).
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Source: Department of Physics
Editor: Guo Lili
