Physical Review Letters reports ICQM Faculty Member Wei Han and collaborators’ work on experimental progress of magnetic 2DEG in oxide heterostructures

In recent years, two-dimensional electron gas residing in oxide heterostructures exhibit a great potential in applications. Ultra-high mobility and superconducting make 2DEGs present in LaAlO₃/SrTiO₃ an ideal study platform. Via interfacial engineering, magnetic 2DEGs could be realized and could pave the way for developing functional spintronics devices. Compared to conventional 2DEGs based on SrTiO₃, EuO is a ferromagnetic insulator. As a result, EuO-based 2DEGs could display clear magnetic behaviors, such as magnetoresistance (MR), anomalous Hall effect (AHE) et al, as a result of interface proximity effect.

In this recent work published in Physical Review Letters, Wei Han’s group, collaborated with Jirong Sun’s group from IOP, makes an important progress in oxide heterostructures consisting of EuO and KTaO₃. Clear magnetic transport behaviors have been observed in this novel magnetic 2DEGs. Molecular beam epitaxy is used to grow EuO/KTaO₃ heterostructures, as indicated in Fig. (a). Based on the transport results obtained from Van der Pauw method, the mobility could reach 111 cm²/Vs at 2K, as shown in in Fig. (b). When applying magnetic field, MR and AHE could be observed. Due to the relatively high Curie temperature and strong magnetic moment of EuO, AHE in this 2DEGs could be observed up to 50K, as shown in Fig. (c). Both the MR and AHE are clear evidences of the magnetic 2DEG formed between EuO and KTaO₃. Based on the results of density-functional theory calculations, the TaO₂ layer is driven into a ferromagnetic state through interlayer exchange by neighboring EuO, thus making interfacial 2DEGs magnetic.

The observation of high-mobility magnetic 2DEGs residing in EuO/ KTaO₃ heterostructures contributes to the study of magnetism in 2DEGs and could pave the way for exploring functional devices in spintronics.

Figure: Growth and characterizations of magnetic 2DEGs in oxide heterostructures: (a) Schematic illustrations of EuO/ KTaO₃ heterostructures grown by molecular beam epitaxy. (b) Temperature dependence of the electron mobility in magnetic 2DEGs. (c) Anomalous Hall effect in magnetic 2DEGs.

This work has been published in Physical Review Letters on September 12th, 2018 (Phys. Rev. Lett. 121, 116803, (2018)). DOI: https://doi.org/10.1103/PhysRevLett.121.116803. These authors, Hongrui Zhang from IOP, Yu Yun, post-doc from ICQM, and Xuejing Zhang from IOP are co-first authors. Prof. Wei Han and Prof. Jirong Sun from IOP are the corresponding authors. The research is financially supported by National Basic Research of China, the National Natural Science Foundation of China and the Key Program of the Chinese Academy of Sciences.