Spin Dynamics of Topological Spin Textures in Chiral Magnets

Who: Emrah Turgut, Cornell University
Thursday, January 25, 2018 - 4:30pm to 5:30pm
DH  A200

The chiral spin textures are a consequence of the anti-symmetric exchange interaction, which presents in the material systems with broken inversion symmetry, such as B20FeGe. This interaction enables chiral magnetic order, including topologically non-trivial magnetic skyrmions, which display rich new magnetic phenomena and require low critical current densities to manipulate.  This makes magnetic skyrmions a promising platform for power-efficient spintronics applications. Therefore, a deeper understanding of the static and dynamic magnetic properties of these materials will be a key step toward their application in spintronic devices. In this talk, I will present our study of both sputtered, epitaxial B20 FeGe and B20 FeGe grown using vapour transport. In particular, I will discuss microwave absorption spectroscopy (MAS)of bulk, single crystal FeGe with which we identify the spin dynamics of all magnetic phases. These results reveal the critical role of substrate-induced strain on the magnetic phases of B20 FeGe.  To gain better control overstrain and to tune the strength of anti-symmetric exchange, I grew B20 FeGe and MnxFe1-xGeon Si with MBE. After characterization using electron and X-ray diffraction,magnetometry, and cryo-Lorentz-STEM imaging, we study MAS of these films. We identify a new spin wave mode along the film thickness, with a wavelength that matches its helical period, enabling a new, simple method of quantitatively characterizing the anti-symmetric exchange.