Giant Anisotropic\nMagnetoresistance in Few-Layer α‑RuCl<sub>3</sub> Tunnel\nJunctions

The spin–orbit-assisted Mott insulator α-RuCl<sub>3</sub> is proximate to the coveted quantum spin liquid (QSL) predicted\nby the Kitaev model. In the search for the pure Kitaev QSL, reducing\nthe dimensionality of this frustrated magnet by exfoliation has been\nproposed as a way to enhance magnetic fluctuations and Kitaev interactions.\nHere, we perform angle-dependent tunneling magnetoresistance (TMR)\nmeasurements on ultrathin α-RuCl<sub>3</sub> crystals with various\nlayer numbers to probe their magnetic, electronic, and crystal structures.\nWe observe a giant change in resistance, as large as ∼2500%,\nwhen the magnetic field rotates either within or out of the α-RuCl<sub>3</sub> plane, a manifestation of the strongly anisotropic spin interactions\nin this material. In combination with scanning transmission electron\nmicroscopy, this tunneling anisotropic magnetoresistance (TAMR) reveals\nthat few-layer α-RuCl<sub>3</sub> crystals remain in the high-temperature\nmonoclinic phase at low temperatures. It also shows the presence of\na zigzag antiferromagnetic order below the critical temperature <i>T</i><sub>N</sub> ≃ 14 K, which is twice the one typically\nobserved in bulk samples with rhombohedral stacking. Our work offers\nvaluable insights into the relation between the stacking order and\nmagnetic properties of this material, which helps lay the groundwork\nfor creating and electrically probing exotic magnetic phases such\nas QSLs via van der Waals engineering.