Charge ordering, ferroelectric, and magnetic domains in LuFe2O4 observed by scanning probe microscopy

Abstract

LuFe2O4 is a multiferroic system which exhibits charge order, ferroelectricity, and ferrimagnetism simultaneously below 230 K. The ferroelectric/charge order domains of LuFe2O4 are imaged with both piezoresponse force microscopy (PFM) and electrostatic force microscopy (EFM), while the magnetic domains are characterized by magnetic force microscopy (MFM). Comparison of PFM and EFM results suggests that the proposed ferroelectricity in LuFe2O4 is not of usual displacive type but of electronic origin. Simultaneous characterization of ferroelectric/charge order and magnetic domains by EFM and MFM, respectively, on the same surface of LuFe2O4 reveals that both domains have irregular patterns of similar shape, but the length scales are quite different. The domain size is approximately 100 nm for the ferroelectric domains, while the magnetic domain size is much larger and gets as large as 1 lm. We also demonstrate that the origin of the formation of irregular domains in LuFe2O4 is not extrinsic but intrinsic.