Giant monolayer magnetization of Fe on MgO: A nearly ideal two-dimensional magnetic system

Studies of the structural, electronic, and magnetic properties of a model 3d ferromagnetic metal-ceramic interface system Fe/MgO(001) by the full-potential linearized augmented-plane-wave total-energy method are reported. Surprisingly, the electronic and magnetic properties of a monolayer of Fe on MgO(001) substrate (magnetic moment M=3.07${\mathrm{\mu }}_{\mathit{B}}$) are remarkably close to that of a free-standing Fe monolayer (with a giant moment M=3.10${\mathrm{\mu }}_{\mathit{B}}$), as a result of the lack of electronic interaction between Fe and MgO. (The charge transfer at the Fe/MgO interface is less than 0.05 e/atom and so any direct chemical interaction between Fe and MgO is unlikely.) Thus, this system might be an ideal two-dimensional system for studying other phenomena such as magnetic anisotropy, phase transitions, and critical behavior. For two layers of Fe on MgO, i.e., 2Fe/MgO(001), the top layer Fe(M=2.96${\mathrm{\mu }}_{\mathit{B}}$) shows features close to that of a free bcc Fe(001) surface (M=2.96${\mathrm{\mu }}_{\mathit{B}}$). Significantly, the magnetic moment of the Fe layer that interfaces the MgO substrate (M=2.85${\mathrm{\mu }}_{\mathit{B}}$) is also largely enhanced from the subsurface moment (2.35${\mathrm{\mu }}_{\mathit{B}}$) in bcc Fe(001), again indicating an extremely weak effect from the MgO substrate.