Magnetic decoupling of Fe coverage across atomic step of MoS₂ flakes on SiO₂ surface

In this study, we deposited Fe films on MoS₂ flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS₂ flakes were fabricated on SiO₂/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS₂ flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS₂ flakes had a mean lateral size of 10-20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS₂/SiO₂, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS₂ flakes. Although the Fe coverage was much thicker than the MoS₂ atomic step height (∼0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS₂ and Fe/SiO₂ were expected, a magnetic decoupling between the magnetic domains of Fe/MoS₂ and Fe/SiO₂ was surprisingly observed. For 3.6 nm Fe/MoS₂, the magnetic coercivity (H _c) was 28 ± 5 Oe, while in contrast, the H _c of 3.6 nm Fe/SiO₂ ranged 58 ± 5 Oe. With a thicker Fe coverage of 7.0 nm, the H _c of Fe/MoS₂ and Fe/SiO₂ converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS₂ atomic step between Fe/MoS₂ and Fe/SiO₂ domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS₂ for future spintronic applications.