Ferroelectricity and weak ferromagnetism of hexagonal ErFe O3 thin films

Hexagonal ErFeO3 thin films fabricated by a pulsed laser deposition method were investigated by x-ray diffraction (XRD) and transmission electron microscopy. No structural phase transition was observed between 20 and 900 K. Ferroelectric D-E hysteresis loops were obtained at room temperature using the double-wave method, and the magnitude of spontaneous polarization was determined to be 200nC/cm2. The existence of superlattice reflections in the XRD indicates that the space group of ErFeO3 thin film is the polar hexagonal P63cm. This result also supports the ferroelectricity at room temperature. Magnetic properties were examined by a superconducting quantum interference device and Mössbauer spectroscopy. Below the Néel temperature of 120 K (TN), a weak ferromagnetism appears along the c axis due to the canting of Fe3+ magnetic moments. Around TN, the imaginary part of dielectric constant shows an anomaly. These results prove h-ErFeO3 thin films to be multiferroic below 120 K.