New functionalities at oxide interfaces: Ultralow-power magnetization switching by orbital selection and high-mobility two-dimensional hole/electron transport
· Invited
Abstract
We present our recent findings: 1) Low-power magnetization control utilizing peculiar electronic structures of magnetic perovskite oxide interfaces [1,2], and 2) realization of a high-mobility two-dimensional “hole” gas (2DHG) and electron gas (2DEG) at an oxide interface [3]. Both results are promising for future oxide-based electronics.
Bias-driven magnetization control of ferromagnets is highly desirable, but still challenging because generally electric-field effect is too weak to induce a large change in the magnetic anisotropy (MA) that is required for magnetization switching. Here, using a magnetic tunnel junction (MTJ) composed of La0.67Sr0.33MnO3 (LSMO)/SrTiO3 (STO)/LSMO, we demonstrate that a drastic change in the MA of LSMO can be induced when the chemical potential EF at the LSMO/STO interface is moved between different orbital symmetry bands [1]. By this new approach, we have successfully realized a magnetic-field-free 90°-magnetization switching of LSMO by applying a small electric field of 0.05 V/nm. With changing V, the MA of the LSMO layer switches from two-fold symmetry to four-fold symmetry when the EF is moved from the eg band to the t2g band. This change of MA is strong enough to rotate the magnetization without any assisting magnetic field, with an extremely small switching current density of ~ 10–2 A/cm2 [2]. Furthermore, we show our recent finding of a 2DHG with ultrahigh mobility up to 24,000 cm2V–1s–1 (at 2 K), which is realized by depositing a sub-nm-thick Fe layer (thickness ≦ 0.2 nm) on an STO surface. This is the highest hole mobility ever reported in oxide materials [3]. We found that the 2DHG/2DEG transport can be switched and controlled by the Fe thickness and gate voltage.
[1] L. D. Anh et al., Sci. Rep. 7, 8715 (2017). [2] L. D. Anh et al., Phys. Rev. Applied 12, 041001 (2019).[3] L. D. Anh et al, Adv. Mater. 32, 1906003 (2020).
Bias-driven magnetization control of ferromagnets is highly desirable, but still challenging because generally electric-field effect is too weak to induce a large change in the magnetic anisotropy (MA) that is required for magnetization switching. Here, using a magnetic tunnel junction (MTJ) composed of La0.67Sr0.33MnO3 (LSMO)/SrTiO3 (STO)/LSMO, we demonstrate that a drastic change in the MA of LSMO can be induced when the chemical potential EF at the LSMO/STO interface is moved between different orbital symmetry bands [1]. By this new approach, we have successfully realized a magnetic-field-free 90°-magnetization switching of LSMO by applying a small electric field of 0.05 V/nm. With changing V, the MA of the LSMO layer switches from two-fold symmetry to four-fold symmetry when the EF is moved from the eg band to the t2g band. This change of MA is strong enough to rotate the magnetization without any assisting magnetic field, with an extremely small switching current density of ~ 10–2 A/cm2 [2]. Furthermore, we show our recent finding of a 2DHG with ultrahigh mobility up to 24,000 cm2V–1s–1 (at 2 K), which is realized by depositing a sub-nm-thick Fe layer (thickness ≦ 0.2 nm) on an STO surface. This is the highest hole mobility ever reported in oxide materials [3]. We found that the 2DHG/2DEG transport can be switched and controlled by the Fe thickness and gate voltage.
[1] L. D. Anh et al., Sci. Rep. 7, 8715 (2017). [2] L. D. Anh et al., Phys. Rev. Applied 12, 041001 (2019).[3] L. D. Anh et al, Adv. Mater. 32, 1906003 (2020).
*This work was supported by Grants-in-Aid for Scientific Research, the JST CREST, and Spin-RNJ.
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Presenters
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Le Duc Anh
- Institute of Engineering Innovation, The University of Tokyo
- Univ of Tokyo