Thickness-dependent magnetic properties in Pt/[Co/Ni]_n multilayers with perpendicular magnetic anisotropy

Abstract 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 nm)/Ni(t Ni nm)]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) ρ xy found that the two serial multilayers with t Co = 0.2 and 0.3 nm have the optimum PMA coefficient K U 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 frequency-dependent linewidth does not depend on Ni thickness and K U. Our results could help promote the PMA [Co/Ni] multilayer applications in various spintronic and spin-orbitronic devices.