Researchers from The University of Manchester have discovered that interfacing magnetic thin films with atomically thin molybdenum disulfide (MoS₂) fundamentally alters how these films dissipate energy - a step toward practical, wafer‑scale 2D spintronic devices.
Using ferromagnetic resonance (FMR) spectroscopy, the team investigated spin pumping and damping mechanisms in large‑area transition‑metal dichalcogenide (TMD)-ferromagnet heterostructures, specifically MoS₂–Ni₀.₈Fe₀.₂ bilayers with varying ferromagnetic thickness. The MoS₂ was grown using chemical vapor deposition (CVD), an industry‑compatible approach that allows uniform monolayer and bilayer coverage across wafer‑scale samples.
By measuring the phenomenological damping parameter, α, the researchers could separate bulk and interfacial (surface) contributions to magnetic energy loss. Typically, an increase in α is associated with spin pumping — the transfer of angular momentum from a ferromagnet into an adjacent non‑magnetic layer. However, the Manchester study reveals that this explanation is incomplete: additional interfacial effects such as spin‑memory loss must also be considered.
When Ni₀.₈Fe₀.₂ (permalloy) was sputtered directly onto monolayer or bilayer MoS₂, the team observed a lower surface contribution to α compared with equivalent films deposited on SiO₂. This reduction in surface damping implies more efficient spin retention at the interface. At the same time, bulk damping increased, which the researchers attributed to changes in the magnetic film’s crystallographic ordering - NiFe grown on MoS₂ exhibited approximately equal proportions of (111) and (220) texture, while NiFe on SiO₂ remained predominantly (111) oriented. The mixed texture leads to enhanced spin‑lattice scattering, increasing intrinsic (bulk) damping.
The corresponding reduction in the surface‑related constant Ksurf aligns with a drop in αₛ, consistent with reduced spin‑memory loss at the NiFe/MoS₂ boundary. This indicates that sputtered permalloy on MoS₂ forms a low‑disorder interface with minimal atomic intermixing - a highly desirable property for spin‑current transport.
To experimentally disentangle these effects, the team varied the Ni₀.₈Fe₀.₂ thickness and used FMR to track the frequency‑dependent linewidth. This approach allowed them to distinguish damping contributions arising from spin pumping and spin‑memory loss at the surface versus spin‑lattice scattering inside the film. Their results clarify why previous studies on 2D material–magnet interfaces have sometimes yielded contradictory outcomes.
Crucially, all measurements were performed on wafer‑scale, CVD‑grown MoS₂ rather than exfoliated flakes, demonstrating that the observed effects are robust and relevant to scalable device technologies. The findings, published in Physical Review Applied, open a route to engineering interfaces where energy loss is selectively minimized - a central requirement for fast, energy‑efficient spintronic memory and logic elements.
“This work is exciting because the fundamental effects a two‑dimensional material can have on magnetic thin films are still largely unexplored,” said Dr. Henry De Libero, lead author and Research Associate in THz Spintronics at The University of Manchester. “We’ve shown how these changes affect energy loss, which is a crucial property for next‑generation memory technologies.”