Extended Data Figure 6: Quantification of the ferroelectric displacements from HAADF-STEM images.
From: Atomically engineered ferroic layers yield a room-temperature magnetoelectric multiferroic
After identifying the position of the lutetium atom with sub-ångström precision, it is compared to the neighbouring atoms and the displacement is calculated. a, Schematics of the ‘down’, ‘up’ and non-polar polarization states. b, Average displacement of the lutetium atoms as a function of the number of LuFeO3 layers m in the (LuFeO3)m/(LuFe2O4)1 structure. The displacement of the end-member LuFeO3 is shown for reference; this displacement of 29 pm corresponds to approximately 4.3 μC cm−2. Error bars in a and b are s.e.m. c, A comparison of the distortion observed in the middle of the LuFeO3 block to those in the edge layers, for example, those adjacent to the LuFe2O4 bilayers. d, In situ TEM heating experiment of the (LuFeO3)m/(LuFe2O4)n superlattices. We infer the ferroelectric phase from where distortions in the lutetium rows are resolved. With increasing temperature, ferroelectricity disappears starting with lower m. Above T = 675 K, we see no ferroelectric distortions; however, the electrical noise in the images at these temperatures is quite large.
