Magnetodynamic properties of ultrathin films of Fe[Formula: see text]Sn[Formula: see text]-a topological kagome ferromagnet.

Fe[Formula: see text]Sn[Formula: see text] is a topological kagome ferromagnet that possesses numerous Weyl points close to the Fermi energy, which can manifest various unique transport phenomena such as chiral anomaly, anomalous Hall effect, and giant magnetoresistance. However, the magnetodynamic properties of Fe[Formula: see text]Sn[Formula: see text] have not yet been explored. Here, we report, for the first time, the measurements of the intrinsic Gilbert damping constant ([Formula: see text]), and the effective spin mixing conductance (g[Formula: see text]) of Pt/Fe[Formula: see text]Sn[Formula: see text] bilayers for Fe[Formula: see text]Sn[Formula: see text] thicknesses down to 2 nm, for which [Formula: see text] is [Formula: see text], and g[Formula: see text] is [Formula: see text]. The films have a high saturation magnetization, [Formula: see text], and large anomalous Hall coefficient, [Formula: see text]. The large values of g[Formula: see text], together with the topological properties of Fe[Formula: see text]Sn[Formula: see text], make Fe[Formula: see text]Sn[Formula: see text]/Pt bilayers useful heterostructures for the study of topological spintronic devices.

Intrinsic anomalous Hall effect in thin films of topological kagome ferromagnet Fe3Sn2.

Fe3Sn2, a kagome ferromagnet, is a potential quantum material with intriguing topological features. Despite substantial experimental work on the bulk single crystals, the thin film growth of Fe3Sn2 remains relatively unexplored. Here, we investigate the effect of two different seed layers (Ta and Pt) on the growth of Fe3Sn2 thin films. We demonstrate the growth of polycrystalline Fe3Sn2 thin films on Si/SiO2 substrates by room temperature sputter deposition, followed by in situ annealing at 500 °C. Our structural and magnetic measurements indicate that a pure ferromagnetic phase is formed for the Pt/Fe3Sn2 thin films with higher saturation magnetization of Ms = 464 emu cc-1, while a mixed-phase (consisting of ferromagnetic, Fe3Sn2 and antiferromagnetic, FeSn) is formed for the Ta/Fe3Sn2 thin films with a lower Ms of 240 emu cc-1. The Pt/Fe3Sn2 thin films also exhibit an anomalous Hall coefficient, Rs ≈ 2.6 × 10-10 Ω cm-1 G-1 at room temperature, which is two order of magnitude higher compared to 3d-transition metal ferromagnets. A non-zero temperature-independent anomalous Hall conductivity σintxy = (23 ± 11) Ω-1 cm-1 indicates an intrinsic mechanism of anomalous Hall effect originating from Berry curvature. These results are important for realizing novel topological spintronic devices on a CMOS-compatible substrate.

Energy-efficient ultrafast nucleation of single and multiple antiferromagnetic skyrmions using in-plane spin polarized current.

We numerically investigate the ultrafast nucleation of antiferromagnetic (AFM) skyrmion using in-plane spin-polarized current and present its key advantages over out-of-plane spin-polarized current. We show that the threshold current density required for the creation of AFM skyrmion is almost an order of magnitude lower for the in-plane spin-polarized current. The nucleation time for the AFM skyrmion is found to be [Formula: see text] ps for the corresponding current density of 1-[Formula: see text]. We also demonstrate ultrafast nucleation of multiple AFM skyrmions that is possible only with in-plane spin polarized current and discuss how the current pulse width can be used to control the number of AFM skyrmions. The results show more than one order of magnitude improvement in energy consumption for ultrafast nucleation of AFM skyrmions using in-plane spin-polarized current, which is promising for applications such as logic gates, racetrack memory, and neuromorphic computing.