Study of magnetic zigzag domain walls and magnetization reversal process in polycrystalline cobalt thin films: Effect of thickness and crystallographic texturing

Abstract

The present work reports the effects of crystallographic texturing on the formation of magnetic zigzag domain walls (DWs) and magnetization reversal process in polycrystalline cobalt thin films of different thickness (10 to 91 nm) deposited by magnetron sputtering technique. Grazing incidence x-ray diffraction measurements, carried out in both in-plane and out-of-plane geometry reveals texturing for thinner thickness (≤ 51 nm) films. Magnetic microstructure and magnetization reversal process is studied with Kerr microscopy by utilizing two in-plane orthogonal sensitivities i.e., longitudinal and transverse sensitivity. It is found that with increasing film thickness, the magnetization reversal process changes significantly. Analysis of angular variation of coercivity reveals that for thinner thickness films (≤ 51 nm), the magnetization reversal process follows two-phase model, also substantiated by the observed magnetic domain structure during reversal process. Nevertheless, it is observed that the zigzag DW angle and magnetization ripple microstructure are found to depend on film thickness. The variation of zigzag DWs angle and magnetic ripple variation is explained in terms of the magnetic anisotropy with the thickness of film employing the crystallographic texturing. Further, we have observed crossover in hysteresis loops measured along for angles ≈20∘ away from the hard axis magnetization. The plausible reason could be due to the superposition of the uniaxial anisotropy generated due to magneto-crystalline anisotropy from the hexagonal phase and biaxial anisotropy generated due to the cubic phase of Co.