Oral: Large anomalous Hall effect, topological Hall effect, skyrmions, and disorder observed in Fe₃GaTe₂

Fe_x(Ge:Ga)Te₂ compounds captivate with their topological electronic and magnetic structure, inherent disorder, and high magnetic transition temperatures. Here, we present findings on the Fe₃GaTe₂ single crystal, which is the newest member of the Fe_x(Ge:Ga)Te₂ compounds. Magnetization data pinpoints a ferromagnetic transition near 360 K. At room temperature, we observed a substantial anomalous Hall resistivity ~ 20 μΩcm and evidence of the topological Hall effect. The Lorentz transmission tunneling microscope unveiled prevalent stripe and skyrmion domain structures above room temperature, hinting at the topological spin texture as an origin of the topological Hall effect. Remarkably, single crystal X-ray diffraction unveiled significant disorder due to the migration of Fe atoms from the intralayer to interlayer positions. We found that annealing at low temperatures effectively mitigates this disorder, leading to decreased resistivity and increased anomalous Hall conductivity. By adjusting the disorder through annealing and analyzing extensive experimental data across a wide range of temperatures and magnetic fields, we delve into the intricate relationship between structural disorder, magnetic structure, and electron transport properties.