5 Search Results

Recently the topic of altermagnetism has attracted tremendous attention, and RuO₂ has been demonstrated to be one of the most promising altermagnetic candidates. However, disputes still remain on the existence of magnetic order in RuO₂. Here in this work, we employ x-ray linear dichroism (XLD), a widely utilized technique for characterizing antiferromagnets, in conjunction with photoemission electron microscopy and multiple scattering calculation to provide clear evidence of the absence of magnetic order in epitaxial RuO₂ films. The observed XLD signal is nearly invariant with temperature and independent of cooling-field direction, in stark contrast to the substantial magnetic-order-related XLD signal predictedmore » by multiple scattering calculation. This finding strongly suggests a nonmagnetic origin for RuO₂. Furthermore, we observed significantly distinct XLD signals at the Ru M₃ and O K edges in RuO₂ films grown on TiO₂ substrate with different surface orientations, which can be attributed to the low-symmetry crystal field. In conclusion, these results unequivocally demonstrate the absence of magnetic order in RuO₂ and establish XLD measurement as a robust technique for probing the low-symmetry magnetic materials.« less

The advent of van der Waals (vdW) ferromagnetic (FM) and antiferromagnetic (AFM) materials offers unprecedented opportunities for spintronics and magneto-optic devices. Combining magnetic Kerr microscopy and density functional theory calculations, the AFM-FM transition is investigated and a surprising abnormal magneto-optic anisotropy in vdW CrSBr associated with different magnetic phases (FM, AFM, or paramagnetic state) is discovered. This unique magneto-optic property leads to different anisotropic optical reflectivity from different magnetic states, permitting direct imaging of the AFM Néel vector orientation and the dynamic process of the AFM-FM transition within a magnetic field. Using Kerr microscopy, not only the domain nucleation andmore » propagation process is imaged but also the intermediate spin-flop state in the AFM-FM transition is identified. In conclusion, the unique magneto-optic property and clear identification of the dynamics process of the AFM-FM phase transition in CrSBr demonstrate the promise of vdW magnetic materials for future spintronic technology.« less

The creation of van der Waals (vdW) ferromagnets with tunable Curie temperature (T_C) and magnetic anisotropy is essential in developing vdW magnet-based devices. Here, we report an effective and reliable method for modulating the magnetic properties of vdW Fe₅GeTe₂ by site-specific Ga⁺ implantation. In this study, we report an easy axis in the ab-plane for bulk Fe₅GeTe₂ (T_C = 310 K) and an axis out of the plane for thin Fe₅GeTe₂ flakes (T_C = 290 K). Combining element-resolved photoemission electron microscopy and spatially resolved magneto-optic Kerr microscopy, we find that the implantation of a tiny amount of 10^–3 Ga⁺·Å^–3 inmore » Fe₅GeTe₂ greatly enhances the T_C from 290 to 360 K and switches the magnetic easy axis from the out-of-plane c axis to the ab-plane. The room-temperature x-ray magnetic circular dichroism signal is enhanced from 0% to 9% at an implantation level of 10^–2 Ga⁺·Å^–3. These results provide new opportunities for tailoring the magnetic properties of vdW materials beyond room temperature.« less

Magnetic skyrmions are topological spin textures, which usually exist in noncentrosymmetric materials where the crystal inversion symmetry breaking generates the so-called Dzyaloshinskii-Moriya interaction. This requirement unfortunately excludes many important magnetic material classes, including the recently found two-dimensional van der Waals (vdW) magnetic materials, which offer unprecedented opportunities for spintronic technology. Using photoemission electron microscopy and Lorentz transmission electron microscopy, we investigated and stabilized Néel-type magnetic skyrmion in vdW ferromagnetic Fe ₃ GeTe ₂ on top of (Co/Pd) _n in which the Fe ₃ GeTe ₂ has a centrosymmetric crystal structure. We demonstrate that the magnetic coupling between the Fe ₃more » GeTe ₂ and the (Co/Pd) _n could create skyrmions in Fe ₃ GeTe ₂ without the need of an external magnetic field. Our results open exciting opportunities in spintronic research and the engineering of topologically protected nanoscale features by expanding the group of skyrmion host materials to include these previously unknown vdW magnets.« less