Abstract :

Ferromagnetic materials break up into magnetic domains separated by magnetic domain walls (DW). The size and configuration of domains and DWs are determined by various properties of the material such as exchange interaction, magnetocrystalline anisotropy, shape anisotropy etc. In recent years, DW based magnetic memory and logic devices are attracting alot of attention due to its tremendous technological relevance. The implementation of these devices critically depends on the control over DW assisted magnetization reversal processes. In the first part of this colloquium the concepts of magnetism, particularly; the formation of domains and DWs in ferromagnetic thin films and nano-structures will be discussed. Then a few case studies will be presented to illustrate the fundamental concepts. At the end some recent experimental results will be presented where we investigate the magnetization reversal by domain wall (DW) injection, pinning and depinning at a geometrical constriction in Permalloy (Py) nanowire (NW) driven by external in-plane magnetic field, using localized electrical probes, along with magnetic domain imaging. We could controllably inject vortex DWs of different chiralities into the nanowire and estimate chirality dependent pinning probability at a nano-constriction in the wire. The interaction of DWs with a notch is investigated through experiments and micromagnetic simulations. The micromagnetic simulations and magnetic domain imaging were complementary to each other. In another example DW motion in perpendicularly magnetized Pt/Co/Pt will be discussed. These results demonstrate the difficulties in achieving deterministic switching behavior, provides a platform to understand the main bottlenecks and suggest possible solutions to circumvent the technological hurdles.

ABOUT THE SPEAKER:

P. S. Anil Kumar obtained Ph.D (Physics) degree in 1998 from University of Pune. He was a Dutch Technology Foundation Post Doctoral Fellow at University of Twente, in The Netherlands until 2000. Then he moved to Max-Planck Institute of Microstructural Physics, Germany with Max-Planck Postdoctoral Fellowship. Subsequently he received the Alexander von Humboldt Research Fellowship. He joined the Department of Physics of Indian Institute of Science in 2004 where he is currently an Associate Professor. His research interests are in Spintronics, Magnetic Nano-structures, Magnetotransport in Metallic Multilayers and Oxides, Magnetic properties of ultra-thin ferromagnets, spin polarized electron scattering etc. He is the recipient of many awards including: Material Research Society (India) Medal (2011), NASI-Scopus Young Scientist Award 2010 (2011), Microsoft Research India outstanding young faculty award (2011), Prof. Y.T. Thathachari Prestigious Research Award for Science (2013), MRSI silver jubilee medal (2014). Young career award in Nano-science and Nano-technology by Department of Science and Technology (2015).