April 2018

Dr. Dmitry Yudin, Seminar “Skyrmion matter: Ferromagnets vs. Antiferromagnets”

4/12/2018
  • PRESENTER:   Dr. Dmitry Yudin

    INSTITUTE:     ITMO University, Saint Petersburg, Russia

    DATE:            Thursday, April 12, 2018

    TIME:             10:00 AM - 11:00 AM

    LOCATION:     Ibn Sina Building B3/L5/R5220


“Skyrmion matter: Ferromagnets vs. Antiferromagnets”​


ABSTRACT

Recent progress in the fabrication of magnetic materials motivated a keen interest towards the studying of particle-like domains, such as magnetic skyrmions. Such non-collinear states may emerge as a result of competition among Heisenberg exchange, antisymmetric Dzyaloshinskii-Moriya interaction, and magnetocrystalline anisotropy in both anti- and ferromagnetic materials. Skyrmions and other topologically protected magnetic textures have been proposed as building blocks for logical operations and information storage in the rapidly advancing fields of magnon spintronics and skyrmionics. In this talk we consider advantages and disadvantages of both anti- and ferromagnetic skyrmions and solitons for potential applications. In particular, we propose to use an external off-resonant pumping as a tool to control Dzyaloshinskii-Moriya interaction in ferromagnetic layers with strong spin-orbit coupling. Combining theoretical analysis with numerical simulations we demonstrate that linearly polarized off-resonant light may help stabilizing novel non-collinear magnetic phases by inducing a strong anisotropy of the Dzyaloshinskii-Moriya interaction as well as to control size, shape and stability of ferromagnetic skyrmions. We further develop an idea of a three-input majority gate on magnetic solitons in quasi-one-dimensional helical magnets. From the other hand, we closely inspect antiferromagnetic skyrmions, namely their lifetime and stability as a function of temperature and external magnetic field. It turns out that such a skyrmion is metastable at zero temperature in a certain parameter range set by two boundaries separating the skyrmion state from the uniform antiferromagnet phase and a stripe domain state. We show that the antiferromagnetic skyrmions are stable on the timescales of milliseconds below 50 K for realistic material parameters, making their experimental investigations viable.



BIOGRAPHY

Dmitry Yudin studied physics at Moscow Institute of Physics and Technology (Moscow, Russia) and graduated with a PhD examination at Uppsala University (Uppsala, Sweden). During his PhD he was jointly supervised by Prof. Olle Eriksson (Uppsala University, Sweden) and Prof. Mikhail Katsnelson (Radboud University Nijmegen, the Netherlands) with the strong emphasis on studying strongly correlated electronic systems, magnetism and spin-dependent phenomena. He contributed to the development of advanced numerical technique, namely dual fermion approach, which allows to generalize a very successful dynamical mean-field theory to include spacial correlations. Another line of research activity he was pursuing at the time is studying of topologically nontrivial spin textures on exotic lattices, e.g. a skyrmion propagating along the edge of kagome lattice. He then took a position as a Research Fellow at Nanyang Technological University (Singapore) and subsequently at the ITMO University (Saint Petersburg, Russia) where he is still employed as a Researcher. He is currently active in developing a unified framework for studying spin-transfer and spin-orbit torques for antiferromagnetic spintronics.