Research Projects

The recent discovery of non-trivial, vortex-like, nano-sized (~ 5 - 200 nm) topological spin solitons named “skyrmions” and their self-organization into a lattice in bulk non-centrosymmetric chiral magnets such as cubic- MnSi, MnSi1-xGex, FeGe, Fe1-xCoxSi, Cu2OSeO3, D2d symmetric Heusler Mn-Pt-Sn systems is an emerging topic in the field of Spintronics. In chiral magnets without inversion symmetry, the Dzyaloshinskii–Moriya interaction (DMI) gradually twists the exchange-driven-ferromagnetic (FM) spin arrangement, thus giving rise to a helical spin ground state. Finite external magnetic fields transform the heli-magnetic structure into a skyrmion lattice near the transition temperatures. Magnetic skyrmions were also observed in metallic heterostructures (Fe/Ir, Co/Pt, SrRuO3/SrIrO3, etc.), where, the interfacial-DMI resulting from the broken inversion symmetry and strong spin-orbit interaction induced by the neighbouring heavy metal play a crucial role in forming the skyrmions lattice and deciding skyrmion size and stability. Skyrmions are envisaged to replace the conventional FM domains of magnetic race-track memory designs. In these devices, binary information (0/1) is encoded in up and down magnetic domains separated by domain walls. Spin-polarized current pulses are used to displace the magnetic domains along the track via the spin-transfer torque mechanism during sensing of the information encoded in domains. Albeit, during the data transmission, the domains require large current densities for their movement (1010-1011 A.m-2), which causes joule heating, thereby failure of the device. In order to avoid this problem, one Novel direction is studying the skyrmions and their movement in skyrmion hosting nanowires (NW) for the application in race-track memory designs, as nanowire systems are the ground for the execution of racetrack memory devices ascribed to their 1-D nature. It is found that skyrmions are efficiently mobilized by current densities of ≈ 106 - 107 Am-2, which are nearly 4 - 5 orders of magnitude lesser than that required for conventional domain walls (DWs) in FM systems. In the NW systems, when the nanocrystallite size/diameter of NW (d) approaches the individual skyrmion size, it is possible to extend the skyrmion lattice phase stabilization over large magnetic fields and temperature ranges. Moreover, large THE signals and modification in the skyrmions resonance frequencies can be expected compared to Bulk systems. Therefore, an investigation of the finite-size effects of NWs/nanoclusters on the skyrmion spin structures is intriguing from the viewpoint of fundamental science and paves the way to the realization of skyrmion host materials for practical applications in spintronics.

Magnetic Materials, Skyrmions, Topological configurations, Nanomaterials, Finite-size effects, Spintronics.