Browsing by Author "Young, David P."

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    Annihilation and Control of Chiral Domain Walls with Magnetic Fields
    (ACS, 2021-02-10) Karna, Sunil K.; Marshall, Madalynn; Xie, Weiwei; DeBeer-Schmitt, Lisa; Young, David P.; Vekhter, Ilya; Shelton, William A.; Kovács, Andras; Charilaou, Michalis; DiTusa, John F.; Physics, School of Science
    The control of domain walls is central to nearly all magnetic technologies, particularly for information storage and spintronics. Creative attempts to increase storage density need to overcome volatility due to thermal fluctuations of nanoscopic domains and heating limitations. Topological defects, such as solitons, skyrmions, and merons, may be much less susceptible to fluctuations, owing to topological constraints, while also being controllable with low current densities. Here, we present the first evidence for soliton/soliton and soliton/antisoliton domain walls in the hexagonal chiral magnet Mn1/3NbS2 that respond asymmetrically to magnetic fields and exhibit pair-annihilation. This is important because it suggests the possibility of controlling the occurrence of soliton pairs and the use of small fields or small currents to control nanoscopic magnetic domains. Specifically, our data suggest that either soliton/soliton or soliton/antisoliton pairs can be stabilized by tuning the balance between intrinsic exchange interactions and long-range magnetostatics in restricted geometries.
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    Topological Hall effect and magnetic states in the Nowotny chimney ladder compound Cr11⁢Ge19
    (American Physical Society, 2021) Li, Yu; Gui, Xin; Khan, Mojammel A.; Xie, Weiwei; Young, David P.; DiTusa, J. F.; Physics, School of Science
    We have investigated the magnetic and charge transport properties of single crystals of the Nowotny chimney ladder compound Cr11⁢Ge19 and mapped out a comprehensive phase diagram reflecting the complicated interplay between the Dzyaloshinskii-Moriya (DM) interaction, the dipolar interaction, and the magnetic anisotropy. We have identified a set of interesting magnetic phases and attributed a finite topological Hall effect to the recently discovered biskyrmion phase. These data also suggest the existence of an antiskyrmion state at finite fields for temperatures just below the magnetic ordering temperature 𝑇𝑐 as indicated by a distinct change in sign of the topological Hall effect. Above 𝑇𝑐, we discovered a region of enhanced magnetic response corresponding to a disordered phase likely existing near the ferromagnetic critical point under small magnetic fields. Strong spin chirality fluctuations are demonstrated by the large value of the topological Hall resistivity persisting up to 1 T, which is most likely due to the existence of the DM interaction. We argue that changes to the topological Hall effect correspond to different topological spin textures that are controlled by magnetic dipolar and DM interactions that vary in importance with temperature.