Magnetic reversal behavior and domain morphology in low-damping CoFeB/Ni multilayers

Perpendicularly magnetized multilayers (MLs) with low magnetic damping and highly periodic stripe domains are promising materials for energy-efficient spintronic and magnonic devices. Here, we investigate the structure, together with the static and dynamic magnetic properties of a polycrystalline sputter-deposited [ CoFeB ( 0.3 nm ) / Ni ( 0.6 nm ) ] 50 ML and compare it to a [ Co ( 0.3 nm ) / Ni ( 0.6 nm ) ] 50 reference stack. Scanning transmission electron microscopy, supplemented by atomic force microscopy, reveals that using a CoFeB/Ni ML yields a more cohesive and denser grain microstructure than in the Co/Ni ML. Our structural results are corroborated by reciprocal-space x-ray reflectivity and x-ray diffraction, further indicating a smoother CoFeB/Ni ML with weakened crystallographic texture and reduced crystalline coherence lengths compared to the Co/Ni ML, while preserving the overall fcc ( 1 1 1 ) growth induced by the Pt seed layer. Vibrating sample magnetometry shows that the CoFeB/Ni ML exhibits weak perpendicular magnetic anisotropy (PMA), resulting in near-zero-remanence isotropic labyrinth stripe domains following out-of-plane saturation and parallel stripe domains after in-plane saturation, consistent with the absence of strong pinning sites. In contrast, the Co/Ni ML exhibits stronger PMA and more pinning-mediated, disordered domain patterns due to its more inhomogeneous microstructure. Field-dependent magnetic force microscopy demonstrates an evolution from labyrinth stripe to dense bubble domain states in the CoFeB/Ni ML, accompanied by a reduction in microscopic return-point memory of the remanent state. Broadband ferromagnetic resonance measurements further disclose a 25 % reduced Gilbert damping parameter α in the CoFeB/Ni ( α = 0.0147 ) compared to the Co/Ni ML ( α = 0.0193 ), along with a massive 370-fold reduction of the inhomogeneous linewidth broadening. The combined structural, magnetic, and dynamic results indicate that using CoFeB suppresses microstructure-induced magnetic inhomogeneities while staying in the PMA regime. These findings identify CoFeB/Ni MLs as a promising platform for perpendicular spintronic devices, combining low magnetic damping, which is beneficial for coherent magnetization dynamics and long-range magnonic signal propagation, with well-defined domain states.