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

Exchange bias has been vital in magnetic storage devices to pin the magnetisation of the ferromagnetic reference layer in a fixed direction. It was extensively studied in thin-film heterostructures, however the origin of exchange bias is not well understood due to the subtle nature of the interfaces. Recent discovery of two-dimensional van der Waals magnetic materials opens up new avenues to scout for origin of exchange bias. Unlike thin-films, atomically sharp interface registry of two-dimensional materials is crucial for this purpose. The primary objective of this project is to do investigations on exchange bias in two-dimensional heterostructures to address the most fundamental at the same time enigmatic question - 'what is the underlying physics that controls exchange bias?!'. For this, the interface domain structure of the ferromagnetic/antiferromagnetic bilayer heterostructure will be investigated employing advanced synchrotron based x-ray photoemission electron microscopy facilities with polarisation control, which is one of the major expertise of the host. Embedded into two work packages, I intend to tackle this problem in two different interface spin configurations by judicious choice of antiferromagnetic layer; (i) parallel coupling of spins with the spins in the antiferromagnetic layer pointing out of the plane and, (ii) perpendicular coupling with the atomic spins of the antiferromagnetic layer lie in the two-dimensional plane. Electric field control of magnetism has been central to the sustainable advancement of spintronic devices. Two-dimensional materials are extremely sensitive to external electrical stimuli and demonstration of a field effect device based on two-dimensional magnetic materials could be remarkable. Taking advantage of the semiconducting/insulator nature of the antiferromagnetic two-dimensional materials, in a separate work package, I will also demonstrate the electric field control of exchange bias by applying a gate voltage.