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Novel chiral spin textures in B20 FeGe films and oxide heterostructures

Adam Ahmed (Department of Physics, Ohio State University)

In my talk, I will discuss our recent discovery of a novel surface spin texture in FeGe/Si(111) thin films known as “chiral bobbers”. These surface confined spin textures have a topological charge of +/- 1 and are a variant of the bulk-like skyrmion. Through a series of magnetic susceptibility measurements, we track the slope as a function of thickness and find a strong inverse thickness dependence consistent with penetration depth of the chiral bobber phase. Micromagnetic simulations corroborate our experimental results by including interfacial Rashba Dzyaloshinskii-Moriya interaction (DMI) in addition to the bulk DMI found in B20 FeGe. This step was motivated by the natural interface provided by the Si substrate.
In the second part of my talk, I would like to discuss measurement and imaging of nanoscale skyrmions in perovskite oxide heterostructures of SrIrO3/SrRuO3 (SIO/SRO) epitaxial films grown on SrTiO3 (100) substrates. We show regions of large topological Hall resistivity and image collections of isolated skyrmions with low-temperature magnetic force microscopy with diameters between 10-20 nm. Remarkably, the region where skyrmion bubbles are present precisely coincides with the topological Hall peaks. Additionally, we present a new high-temperature skyrmion phase not seen before in both bilayer SIO/SRO and single layer SRO films. This suggests the origin of this high temperature skyrmion phase not to originate from Rashba spin-orbit coupling but an interplay between magnetic anisotropy and dipolar fields.

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