Pseudotunnel magnetoresistance in twisted van der Waals FeGeTe homojunctions

小幡 玲二*; 齊藤 英治; 吉川 貴史; 他13名*

Advanced Materials, 37(8), p.2411459_1 - 2411459_11, 2025/02

https://doi.org/10.1002/adma.202411459

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 , such as twisted interfacial Josephson junctions using high-temperature superconductors. Herein, vdW homojunctions of the thin-magnetic flakes, FeGeTe (FGT), with large ranging from 0 to 90 deg, 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 values, revealing that the vdW gap at the junction interface between the twisted FGT layers behaves like a tunnel barrier and the 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 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.