Magnetization dynamics and damping behavior of Co/Ni multilayers with a graded Ta capping layer

Abstract

Magnetization dynamics of a Co/Ni multilayer film capped by a wedged Ta (0.3–1.3 nm) layer were investigated using time-resolved magneto-optic Kerr microscopy. The ferromagnetic resonance was observed for a wide range of magnetic fields in a variety of geometries. Using a macrospin approximation and the Kittel formula to evaluate the relaxation frequency, a significant increase of the effective anisotropy field was observed as the Ta layer thickness is increased. Furthermore, the damping behavior of the magnetization precession also shows a strong dependence on the Ta layer thickness. Using a model to account for variations of the local anisotropy fields, we reproduce the field evolution of the observed damping using a single Gilbert damping parameter for the Co/Ni system. These findings have direct implications for the rational design of novel spintronic devices.

Disentangling factors governing Dzyaloshinskii domain-wall creep in Co/Ni thin films using PtxIr1−x seed layers

“…This results in a linear composition gradient across the substrate surface. Details on the structural characterization of similar Co/Ni multi-layer films can be found in [27]. M − H loops measured using alternating gradient field magnetometry (AGFM) and vibrating sample magnetometry (VSM) across the composition gradient indicate a saturation magnetization, M s ∼ 645kA/m, and in-plane saturation field, µ 0 H k ∼ 1.3T , which has little dependence on Pt x Ir 1−x seedlayer composition (see supplemental information (S1)).…”

Dispersive Stiffness of Dzyaloshinskii Domain Walls

“…Films were determined to have FCC(111) fibre-texture by x-ray diffraction (XRD) with continuous interfaces confirmed by transmission electron microscopy (TEM) as shown in prior work. [20] K ef f was determined from the in-plane saturation field,…”

“…Films were determined to have FCC(111) fibre-texture by x-ray diffraction (XRD) with continuous interfaces confirmed by transmission electron microscopy (TEM) as shown in prior work. [20] K ef f was determined from the in-plane saturation field, µ o H k (= 1T), by alternating gradient field magnetometry (AGFM) and M s = 600kA/m determined from vibrating sample magnetometry (VSM). Studies on domain growth and morphology were performed using a wide-field white light Kerr microscope with an in-plane electromagnet producing static fields up to 300mT and a perpendicular coil producing 1ms pulses up to 20mT.…”