Thickness-driven structural and magnetic evolution in permalloy thin films

Abstract Ferromagnetic thin films based on iron–nickel (FeNi) alloys continue to play a pivotal role in modern spintronic devices owing to their low coercivity, high permeability, and tunable magnetic properties. Among various design parameters, film thickness emerges as a critical factor that governs the interplay between microstructure, interfacial effects, and magnetic response, especially in the nanometer regime where surface phenomena become prominent. In this study, we systematically investigate the structural and magnetic evolution of permalloy thin films with controlled thickness deposited on silicon substrates. Various characterization techniques, including x-ray reflectivity, grazing incidence x-ray diffraction, field emission scanning electron microscopy, vibrating sample magnetometry, and magneto-optical Kerr effect, are employed to elucidate thickness-dependent changes in crystallographic texture, grain morphology, interface quality, and magnetization behavior. Special emphasis is placed on understanding the emergence of exchange bias effects in nominally single-layer permalloy films and how interfacial and surface phenomena contribute to overall magnetic behavior. The findings provide valuable insights into optimizing permalloy thin films for reliable and scalable integration in spintronic devices, magnetic memory, and sensor technologies.