Research Projects

Magnetic skyrmions, nanoscale swirling spin structures with topological protection, have generated enormous attention since they have potential to become the building block of next-generation spintronic devices due to their high-density and energy efficient manipulation. However, over two decades since their discovery, the practical realization of skyrmion-based devices is limited primarily due to skyrmion Hall effect which causes a transverse motion with respect to the direction of applied current. Antiferromagnetic (AFM) skyrmions, two intertwined skyrmions with mutually opposite spins, provides a promising solution by eliminating the skyrmion Hall effect due to net zero topological charge. Additionally, AFM skyrmions have features like reduced magnetic damping, absence of stray fields, and enhanced resonance frequencies, which make them an ideal candidate for next generation spintronic devices. The aim of this project is to predict novel AFM skyrmions in transition-metal (TM) thin films, study and understand their thermal stability for experimental observation and practical applications. Specifically, our plan is to identify three types of AFM skyrmions: (i) intrinsic AFM skyrmions formed on an antiferromagnetic ground state, (ii) bilayer-coupled AFM skyrmions formed by two oppositely coupled ferromagnetic skyrmions in adjacent atomic monolayers, and (iii) synthetic AFM (SAF) skyrmions formed by two ferromagnetic skyrmions coupled opposite to one another through a non-magnetic spacer layer. For possible choice of TM thin films, we plan to explore combinations of 3d/3d/4d, 3d/3d/5d, 4d/3d/4d, 5d/3d/5d, 4d/3d/5d and 5d/3d/4d atomic trilayers on the surface of Ir(111), Rh(111) and Re(0001) substrates. For 3d elements, we focus on Cr, Mn, Fe, and Co; for 4d element on Rh; and for 5d elements on Re and Ir. These choices include films where skyrmions have already been observed as well as unexplored films. Our research plan is to first calculate the magnetic interactions, such as exchange coupling, Dzyaloshinskii-Moriya interaction (DMI), and magnetic anisotropy energy (MAE), in all the above thin films using density functional theory (DFT) and identify promising ones. For these selected films, we further investigate the formation of AFM skyrmions and also study their thermal stability in presence of external magnetic fields using atomistic spin dynamics (ASD) simulations based on a DFT-parameterized spin Hamiltonian. The outcome of this project is to predict promising TM thin films capable of hosting stable AFM skyrmions which would provide the experimentalists a robust platform to observe these complex spin structures. In addition, our study also provide a guideline to search for new tailored systems. Therefore, this project contributes to the advancement of this emerging field and development of next-generation spintronic devices.