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We systematically investigated the Ni and Co thickness-dependent perpendicular magnetic anisotropy (PMA) coefficient, magnetic domain structures, and magnetization dynamics of Pt(5 nm)/[Co(t Co)/Ni(t Ni)]5/Pt(1 nm) multilayers by combining the four standard magnetic characterization techniques. The magnetic-related hysteresis loops obtained from the field-dependent magnetization M and anomalous Hall resistivity (AHR) ρxy showed that the two serial multilayers with t Co = 0.2 nm and 0.3 nm have the optimum PMA coefficient K U as well as the highest coercivity H C at the Ni thickness t Ni = 0.6 nm. Additionally, the magnetic domain structures obtained by magneto-optic Kerr effect (MOKE) microscopy also significantly depend on the thickness and K U of the films. Furthermore, the thickness-dependent linewidth of ferromagnetic resonance is inversely proportional to K U and H C, indicating that inhomogeneous magnetic properties dominate the linewidth. However, the intrinsic Gilbert damping constant determined by a linear fitting of the frequency-dependent linewidth does not depend on the Ni thickness and K U. Our results could help promote the PMA [Co/Ni] multilayer applications in various spintronic and spin-orbitronic devices. [ABSTRACT FROM AUTHOR]

Among the layered two-dimensional ferromagnetic materials (2D FMs), due to a relatively high TC, the van der Waals (vdW) Fe3GeTe2 (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 (K1) 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 K1 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 TC. We have found large magnetic damping with the effective damping constant αeff ∼ 0.58 along with a broad linewidth (Δ Hpp > 1000 Oe at 9.48 GHz, H ∥ c-axis). Our results provide useful dynamics information for the development of FGT-based spintronic devices. [ABSTRACT FROM AUTHOR]

Among the layered two-dimensional ferromagnetic materials (2D FMs), due to a relatively high TC, the van der Waals (vdW) Fe3GeTe2 (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 (K1) 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 K1 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 TC. We have found large magnetic damping with the effective damping constant αeff ∼ 0.58 along with a broad linewidth (Δ Hpp > 1000 Oe at 9.48 GHz, H ∥ c-axis). Our results provide useful dynamics information for the development of FGT-based spintronic devices. [ABSTRACT FROM AUTHOR]