Thickness and Field-dependent evolution ofmagnetic domains in ferrimagnetic TbFe thin films

Rare-earth–transition-metal ferrimagnetic thin films have emerged as a versatilematerial platform for spintronic and magnetic memory technologies, owingto their rich magnetic domain behavior and the ability to engineer perpendicularmagnetic anisotropy (PMA). Although magnetic reversal and domaindynamics can be tailored through multilayer architectures and interface modification,the extent to which film thickness alone can modulate domain evolutionand magnetization-reversal pathways in single-layer ferrimagnets remains insufficientlyexplored. In this work, we examine the combined influence of filmthickness and an externally applied out-of-plane (OOP) magnetic field on thedomain dynamics and magnetization reversal mechanisms of single-layer TbFeferrimagnetic films. TbFe films of 30 and 100 nm thicknesses were depositedby electron-beam evaporation and systematically characterized using vibrational samplemagnetometry (VSM) and magnetic force microscopy (MFM). Magnetometrymeasurements revealed strong PMA in both samples, accompanied bywasp-waisted OOP hysteresis loops, characteristic of exchange-coupled magneticsublattices. MFM revealed labyrinthine domain patterns in both films. Upon theapplication of positive OOP magnetic field, both films undergo complete magnetizationreversal, where switching dynamics differ markedly. The 30 nm filmexhibits an abrupt reversal accompanied by a narrow and symmetric switching fielddistribution, whereas the 100 nm film reverses gradually through viscousdomains and with broader switching-field distribution. Field-dependent domainimaging further shows distinct and asymmetric domain-evolution pathways, consistentwith a Kondorsky-type reversal mechanism. XPS depth profiling of filmrevealed pronounced compositional inhomogeneity and Fe/Tb imbalance, directly linking chemical inhomogeneity, defect-mediated pinning, and sublattice-specificanisotropy that govern the observed reversal asymmetry. These results highlightthe combined effects of film thickness and external magnetic fields on TbFedomain dynamics, guiding the design of single-layer ferrimagnetic thin filmswith precise domain control and reversible switching for memory and spintronicapplications.