Amorphization-induced Mott-like transition in van der Waals ferromagnets CrGeTe<sub>3</sub> and CrSiTe<sub>3</sub>

ORAL

Abstract

Increasing the Curie temperature (Tc) of van der Waals ferromagnets has long been a highly regarded research topic for developing their applications in spintronic devices. In recent years, the Tc of 2D semiconductors CrGeTe3 (CGT) and CrSiTe3 (CST) has been enhanced through several methods such as external pressure [1] and carrier doping [2]. In addition, CGT and CST are charge-transfer type Mott insulators and an insulator-metal transition occurs simultaneously with the increase in Tc. In this talk, we report that the amorphous CGT and CST created by high-energy ion irradiation surprisingly exhibit similar high-Tc ferromagnetic metallic behavior. Magnetization and transport measurements revealed that the ferromagnetic semiconductor CST (CGT) transforms into a ferromagnetic metal after amorphization, with its Tc increasing from 32K (67 K)to 100K (200K [3]). Local structural analysis using XAFS measurements revealed that the Cr-Te-Cr bonding persists in the amorphous state, but the Cr-Te bond length is shorter than that of crystalline phase. The shortened bond length can modify the super-exchange interaction, resulting in enhanced conductivity and increased Tc, similar to the Mott transition observed under external pressure in single crystals [1].

[1] D. Bhoi, J. Gouchi, N. Hiraoka, Y. Zhang, N. Ogita, T. Hasegawa, K. Kitagawa, H. Takagi, K. H. Kim, Y. Uwatoko, Phys. Rev. Lett. 127, 217203 (2021)

[2] I. A. Verzhbitskiy, H. Kurebayashi, H. Cheng, J. Zhou, S. Khan, Y. P. Feng, G. Eda, Nat Electron 3, 460 (2020)

[3] S. Zhang, K. Harii, T. Yokouchi, S. Okayasu, and Y. Shiomi, Adv. Electron. Mater. 10, 2300609 (2024).

*The irradiation experiments were performed at the tandem accelerator at Japan Atomic Energy Agency with the approval of Proposal No. 2024SC02. X-ray absorption fine structure (XAFS) measurements were performed at the Photon Factory at High Energy Accelerator Research Organization with the approval of Proposal No. 2024P004. A part of this work was carried out by the joint research of the Cryogenic Research Center, the University of Tokyo. This work was supported by JST FOREST Program, Grant Number JPMJFR203H, and by JSPS KAKENHI, Grant Numbers JP23K26525, JP24H01177, JP24K21726, and JP24K00566.

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Publication: S. Zhang, K. Harii, T. Yokouchi, S. Okayasu, and Y. Shiomi, Adv. Electron. Mater. 10, 2300609 (2024).

Presenters

  • Siyue Zhang

    • The University of Tokyo

Authors

  • Siyue Zhang

    • The University of Tokyo

  • Kazuya Harii

    • Quantum Materials and Applications Research Center, National Institutes for Quantum Science and Technology

  • Yasuhiro Niwa

    • High Energy Accelerator Research Organization. The Graduate University for Advanced Studies

  • Tomoyuki Yokouchi

    • Univ of Tokyo
    • RIKEN

  • Takuya Kawada

    • Univ of Tokyo
    • The University of Tokyo

  • Satoru Okayasu

    • Advanced Science Research Center, Japan Atomic Energy Agency

  • Yuki Shiomi

    • Univ of Tokyo
    • The University of Tokyo