Exploring Interfacial Effects in Transition Metal Dichalcogenide/Ferrimagnetic Alloy Heterostructures

Ultrathin ferrimagnetic heterostructures have emerged as promising platforms for next-generation spintronic devices, yet the role of two-dimensional substrates in modulating their magnetic properties remains underexplored. Here, we report a comprehensive study of the thickness- and temperature-dependent magnetic behavior of amorphous Fe73Co8Gd19 films (4–32 nm) deposited on Si, WSe2 bilayer, and WSe2 monolayer substrates. Structural integrity and stoichiometry were confirmed via X-Ray Diffraction (XRD), X-Ray Reflectivity (XRR), Raman spectroscopy, and Energy-Dispersive Spectroscopy (EDS) analysis. In-plane magnetometry from 10–300 K reveals that monolayer WSe2 promotes stronger interfacial spin alignment, with the 4 nm film exhibiting a sharp increase in coercivity below 50 K, where Hc exceeds 23 mT and even surpasses thicker counterparts, alongside enhanced saturation magnetization (∼790 kA/m at 100 K). This dramatic enhancement of coercivity is the most significant result of this work, underscoring the dominant role of interfacial coupling in governing low-temperature magnetic hardness. Conversely, films on bilayer exhibit suppressed magnetization and soft magnetic behavior (Hc < 10 mT) across all temperatures, making them attractive for ultralow-power and high-speed spintronic applications. These findings demonstrate that atomically thin WSe2 interfaces can modulate coercivity, magnetization, and squareness through proximity effects, establishing a tunable and thermally stable platform for spintronic device applications.