Emergent phenomena and device applications in magnetic van der Waals heterostructures

Abstract

Van der Waals (vdW) heterostructures built by the vertical stacking of various 2D materials provide an ideal platform for the rational design of emergent phenomena and device applications. The recent discovery of atomically thin magnetic vdW materials has created new opportunities to explore 2D magnetism in magnetic vdW heterostructures. In this thesis, we will present an exploration into the 2D magnet chromium triiodide (CrI3) and its vdW heterostructures. We will first introduce the unique layer-dependent magnetism in CrI3 enabled by the antiferromagnetic interlayer coupling. We then achieve giant tunneling magnetoresistance by using CrI3 as a tunnel barrier in vdW spin-filter magnetic tunnel junctions. In a dual-gated structure, a pair of bistable magnetic states in four-layer CrI3 can be switched reversibly by electrostatic gating, demonstrating a new kind of voltage-controlled vdW spintronic device. We will also unravel the stacking-dependent magnetism in CrI3, and realize the control of interlayer magnetism and switching of magnetic states via pressure tunning of layer stacking. Finally, we will discuss the helicity-dependent photocurrent in CrI3 and its interplay with the underlying exciton states and magnetic order.