ExBiaVdW · Exchange bias in two-dimensional van der Waals heterostructures

Exchange bias in two-dimensional van der Waals heterostructures

Magnetic materials play a pivotal role in our modern world, enabling technologies that range from hard disk drives to magnetic sensors in smartphones and vehicles. A key breakthrough in this domain was the discovery of exchange bias, a magnetic phenomenon that allows engineers to control the orientation of magnetic domains in thin films with great precision. This control is essential for reliable data storage and sensing, and it revolutionized the magnetic recording industry in the late 1990s—laying the foundation for today’s high-density storage devices. Exchange bias typically arises at the interface between two types of magnetic materials: a ferromagnet (FM)—where magnetic moments align in the same direction—and an antiferromagnet (AFM)—where adjacent magnetic moments cancel each other out. When these materials are layered together, interactions at their interface can “pin” the magnetic direction of the ferromagnet, stabilizing it against external magnetic fields. This asymmetric behavior, known as exchange bias, has been harnessed for decades in magnetic read heads and spintronic devices. However, traditional exchange bias systems rely on bulk thin films grown using high-temperature, high-vacuum techniques. These interfaces often suffer from roughness, strain, and unwanted and difficult to control chemical reactions, which complicate device performance and limit miniaturization. This changed dramatically with the advent of van der Waals (vdW) materials—a new class of atomically thin crystals that can be stacked like LEGO blocks without concern for lattice mismatch. The groundbreaking discovery of graphene in 2004 (which won the Nobel Prize in Physics in 2010) demonstrated that 2D materials can exhibit extraordinary properties when isolated from their 3D bulk forms. Since then, researchers have identified an entire family of vdW materials—including semiconductors, insulators, and more recently, magnetic materials. In 2017, the first magnetic van der Waals materials were discovered that order down to the monolayer limit, ushering in a new era for magnetism at the atomic scale. Unlike conventional thin films, vdW magnets can be exfoliated down to a single layer, maintain clean interfaces without strain, and can be freely combined to form heterostructures—stacks of 2D materials with tailored properties. These heterostructures open new possibilities for designing magnetic systems with unprecedented control over interlayer coupling and spin interactions. Despite these exciting advances, the nature of exchange bias in vdW heterostructures remains poorly understood. Unlike in conventional systems, vdW materials offer new degrees of freedom: spins can lie in-plane or out-of-plane, interfaces can be tuned atom-by-atom, and magnetic properties can be controlled using electric fields, strain, or twist angles between layers. In this context, ExBiaVdW commits to illuminating this less explored yet exciting field of spintronics research by the following key objectives: 1. Fundamental Investigation of Exchange Bias in van der Waals Heterostructures: We aim to uncover the microscopic origins of exchange bias in 2D systems, distinguishing intrinsic interfacial effects from extrinsic factors such as oxidation or defects. 2. Exploration of Spin Configuration Effects: By systematically studying systems where the ferromagnet and antiferromagnet have either parallel (collinear) or perpendicular (orthogonal) spin orientations, we will determine how spin geometry affects exchange bias strength and stability. 3. Modulation of Exchange Bias via Interfacial and External Controls: Investigate how exchange bias can be tuned through interfacial engineering, layer thickness variation, and external stimuli such as electric fields or gating. This could lead to reconfigurable magnetic devices for future spintronic and quantum technologies.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз