Pseudotunnel Magnetoresistance in Twisted van der Waals Fe3GeTe2 Homojunctions

Reiji Obata; Haiming Sun; Kartik Samanta; Naafis Ahnaf Shahed; Mioko Kosugi; Takashi Kikkawa; Alaa Abdallah; Kenji Watanabe; Takashi Taniguchi; Kazu Suenaga; Eiji Saitoh; Shigeo Maruyama; Kazuhiko Hirakawa; Kirill D Belashchenko; Evgeny Y Tsymbal; Junji Haruyama

doi:10.1002/adma.202411459

Pseudotunnel Magnetoresistance in Twisted van der Waals Fe₃GeTe₂ Homojunctions

Adv Mater. 2025 Jan 5:e2411459. doi: 10.1002/adma.202411459. Online ahead of print.

Authors

Reiji Obata¹, Haiming Sun², Kartik Samanta³, Naafis Ahnaf Shahed³, Mioko Kosugi¹, Takashi Kikkawa⁴, Alaa Abdallah¹, Kenji Watanabe⁵, Takashi Taniguchi⁶, Kazu Suenaga², Eiji Saitoh^{3

7

8

9}, Shigeo Maruyama¹⁰, Kazuhiko Hirakawa¹¹, Kirill D Belashchenko³, Evgeny Y Tsymbal³, Junji Haruyama^{1

11}

Affiliations

¹ Faculty of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa, 252-5258, Japan.
² The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka, 567-0047, Japan.
³ Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA, 68588.
⁴ Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
⁵ Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁶ Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
⁷ Institute for AI and Beyond, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
⁸ WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
⁹ Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki, 319-1195, Japan.
¹⁰ Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
¹¹ Institute for Industrial Sciences, The University of Tokyo, 4-6-1 Komaba Meguro-ku, Tokyo, 153-8505, Japan.

PMID: 39757443
DOI: 10.1002/adma.202411459

Abstract

Twistronics, a novel engineering approach involving the alignment of van der Waals (vdW) integrated two-dimensional materials at specific angles, has recently attracted significant attention. Novel nontrivial phenomena have been demonstrated in twisted vdW junctions (the so-called magic angle), such as unconventional superconductivity, topological phases, and magnetism. However, there have been only few reports on integrated vdW layers with large twist angles θ_t, such as twisted interfacial Josephson junctions using high-temperature superconductors. Herein, vdW homojunctions of the thin-magnetic flakes, Fe₃GeTe₂ (FGT), with large θ_t ranging from 0° to 90°, without inserting any tunnel barriers are assembled. Nevertheless, these vdW homojunctions exhibit tunnel-magnetoresistance (TMR) like behavior (pseudo-TMR (PTMR) effect) with the ratios highly sensitive to the θ_t values, revealing that the vdW gap at the junction interface between the twisted FGT layers behaves like a tunnel barrier and the θ_t serves a control parameter for PTMR by drastically varying magnitudes of the lattice-mismatch and the subsequent appearance of antiferromagnetic (AFM) spin alignment. First-principles calculations considering vacuum gaps indicate strong dependence of TMR on the θ_t driven by the sixfold screw rotational symmetry of bulk FGT. The present homojunctions hold promise as a platform for novel AFM spin-dependent phenomena and spintronic applications.

Keywords: large angle twistronics; lattice mismatch; magnetic thin layers; magnetic tunnel junctions; van der Waals gaps.

Abstract

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