Visualizing weak ferromagnetic domains in multiferroic hexagonal ferrite thin film

We report cryogenic magnetic force microscopy (MFM) studies of a 200-nm-thick hexagonal (h) LuFeO3 film grown by molecular-beam epitaxy on a (111)-oriented yttria-stabilized cubic-zirconia substrate. Labyrinthlike domains ∼1.8μm in size were observed after zero-field cooling below the Néel temperature, TN≈147 K, where weak ferromagnetic order (P63cm) with a canted moment of MS≈0.02μB/f.u. exists. At 6 K, MFM images of the magnetization reversal process reveal a typical domain behavior of a pinning-dominated hard magnet. The pinning strength is substantially reduced at elevated temperature. The temperature dependence of the domain contrast demonstrates that our MFM is able to detect the domain contrast of magnets with tiny magnetic moments (∼0.002μB/f.u.). An upper limit of the linear magnetoelectric coefficient of h-LuFeO3 (αzz<6ps/m) is estimated by magnetoelectric force microscopy measurements.