Exploring thickness effects on magnetization reversal mechanism and domain state configuration in ferrimagnetic Gd–Fe thin film

This paper provides an in-depth investigation of thickness effects on magnetization reversal mechanism and magnetic domain state interactions in Gd–Fe thin films using the first-order reversal curve (FORC) and Magneto-optic Kerr effect (MOKE). Structural analysis reveals the formation of Fe nanocrystalline structures over the amorphous Gd–Fe matrix. Magnetization measurements possess a strong in-plane (IP) magnetic anisotropy across all films. The IP FORC investigations through 2D contour plots show a clear transition from a strongly interacting multi-domain (MD) state to a weakly interacting MD and single-domain (SD) state as thickness increases from 10 to 60 nm. Analysis of switching field distribution indicates a peak broadening with enhanced inter-grain interactions on increasing thickness. The MOKE measurements show a transition from zigzag walls to cross-tie walls in the 10 nm film, and ripple-like domain walls are observed in the 30 nm film, suggesting magnetization reversal is primarily governed by MD states. In contrast, a transition from alternating band domains to SD state is observed in the 40 and 60 nm films. Angular variations in the domain pattern confirm that the nucleation and propagation of domain walls predominantly govern the reversal mechanism. Micromagnetic simulations were conducted to validate and support the experimental results.