Research Areas

  • Spintronics and Nanomagnetics
    Dr. Kuntal Roy
    kuntal[AT]iiserb.ac.in

    Electron's spin-based counterpart, so-called “Spintronics” exploits the quantum-mechanical spin of an electron to store, process, and communicate information. The 2007 Nobel Prize in Physics (awarded to Fert and Grunberg for the discovery of Giant Magnetoresistance in magnetic multilayers) recognizes the remarkable transition of spintronics from fundamental studies to a critical device technology. Spintronics has profound potential to be the replacement of current transistor-based technology in our future energy-efficient information processing systems. In fact, magnetic memories are being commercially manufactured for computers, cars, mission to Mars etc.

    Although there is no Ohmic loss due to flow of charge in spintronic devices, unlike in charge-based transistors, the energy dissipation to switch magnetization in spintronic devices can be higher than that of transistors, if we use magnetic field or spin-polarized current to switch the spins. However, if we use electric field to switch the magnetization in strain-mediated piezoelectric-magnetostrictive multiferroic composites, with a suitable choice of materials and dimensions, the energy dissipation can be reduced to a miniscule amount of ~1 attojoule in sub-nanosecond switching delay at room-temperature [Switching up spin, Nature, Research Highlights (Physics) 476, 375 (25 Aug 2011)].

    Also, an ongoing challenge in the field of multiferroic materials in single-phase is to understand new mechanisms and to realize new materials with correct parameters for application purposes, e.g., energy barrier for polarization/magnetization, room-temperature operation, damping. The giant spin-Hall effect and giant spin-orbit torque from the surface states of topological insulators (the 2016 Nobel Prize in Physics was awarded to Thouless, Haldane, and Kosterlitz for theoretical discoveries of topological phase transitions and topological phases of matter) are very active area of research globally now-a-days too.

    On theory and simulation, Density Functional Theory (DFT) [the 1998 Nobel Prize in Chemistry, awarded to Kohn and Pople] based ab initio studies, spin transport using Non-Equilibrium Green Function (NEGF) formalism [which has been proved fruitful for demonstrating quantum effects in nanoscale], and stochastic Landau-Lifshitz-Gilbert (LLG) equation of magnetization dynamics [hand-written MATLAB code for critical understandings] can be utilized. On experimental side, for the fabrication of such spin-devices, it requires several state-of-the-art facilities e.g., Scanning Electron Microscope (SEM), Electron Beam Lithography (EBL), Vibrating Sample Magnetometer (VSM), Magnetic Force Microscopy (MFM), Pulsed laser deposition (PLD), E-Beam Evaporation.

    This is an interdisciplinary field of research with different streams of science and engineering involved e.g., Electrical and Computer Engineering, Physics, Chemistry, Materials Science and Engineering, Nanoscale Science and Engineering. Some other research topics, but not limited to, are the following.

    • Landauer limit of energy dissipation in spin devices
    • Ultrafast optical magnetization switching
    • Ultrasensitive magnetic sensors
    • Skyrmions
    • Magnetic insulators
    • Magnetic tunnel junctions
    • Neuromorphic spin devices and computing
    • Spin-transfer-torque and spin pumping
    • Spin oscillators
    • Magnetocaloric materials
    • Organic spintronics
    • Spin circuits for developing systems and architectures