Magnetic dynamics of two-dimensional itinerant ferromagnet Fe_(3)GeTe_(2)

Among the layered two-dimensional ferromagnetic materials(2D FMs),due to a relatively high T_(C),the van der Waals(vdW)Fe_(3)GeTe_(2)(FGT)crystal is of great importance for investigating its distinct magnetic properties.Here,we have carried out static and dynamic magnetization measurements of the FGT crystal with a Curie temperature TC≈204 K.The M-H hysteresis loops with in-plane and out-of-plane orientations show that FGT has a strong perpendicular magnetic anisotropy with the easy axis along its c-axis.Moreover,we have calculated the uniaxial magnetic anisotropy constant(K_(1))from the SQUID measurements.The dynamic magnetic properties of FGT have been probed by utilizing the high sensitivity electron-spin-resonance(ESR)spectrometer at cryogenic temperatures.Based on an approximation of single magnetic domain mode,the K_(1)and the effective damping constant(αeff)have also been determined from the out-of-plane angular dependence of ferromagnetic resonance(FMR)spectra obtained at the temperature range of 185 K to T_(C).We have found large magnetic damping with the effective damping constantαeff~0.58 along with a broad linewidth(ΔH_(pp)>1000 Oe at 9.48 GHz,H||c-axis).Our results provide useful dynamics information for the development of FGT-based spintronic devices.

Temperature-and field angular-dependent helical spin period characterized by magnetic dynamics in a chiral helimagnet MnNb_(3)S_(6)

The chiral magnets with topological spin textures provide a rare platform to explore topology and magnetism for potential application implementation.Here,we study the magnetic dynamics of several spin configurations on the monoaxial chiral magnetic crystal MnNb_(3)S_(6)via broadband ferromagnetic resonance(FMR)technique at cryogenic temperature.In the high-field forced ferromagnetic state(FFM)regime,the obtained frequency f vs.resonance field H_(res) dispersion curve follows the wellknown Kittel formula for a single FFM,while in the low-field chiral magnetic soliton lattice(CSL)regime,the dependence of H_(res) on magnetic field angle can be well-described by our modified Kittel formula including the mixture of a helical spin segment and the FFM phase.Furthermore,compared with the sophisticated Lorentz micrograph technique,the observed magnetic dynamics corresponding to different spin configurations allow us to obtain temperature-and field-dependent proportion of helical spin texture and helical spin period ratio L(H)/L(0)via our modified Kittel formula.Our results demonstrated that fieldand temperature-dependent nontrivial magnetic structures and corresponding distinct spin dynamics in chiral magnets can be an alternative and efficient approach to uncovering and controlling nontrivial topological magnetic dynamics.