Ferroelectricity and weak ferromagnetism of hexagonalErFeO3thin films

Abstract

Hexagonal $\mathrm{ErFe}{\mathrm{O}}_{3}$ 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 $D\ensuremath{-}E$ hysteresis loops were obtained at room temperature using the double-wave method, and the magnitude of spontaneous polarization was determined to be $200\phantom{\rule{0.16em}{0ex}}\mathrm{nC}/\mathrm{c}{\mathrm{m}}^{2}$. The existence of superlattice reflections in the XRD indicates that the space group of $\mathrm{ErFe}{\mathrm{O}}_{3}$ thin film is the polar hexagonal $P{6}_{3}cm$. This result also supports the ferroelectricity at room temperature. Magnetic properties were examined by a superconducting quantum interference device and M\ossbauer spectroscopy. Below the N\'eel temperature of 120 K $({T}_{\mathrm{N}})$, a weak ferromagnetism appears along the $c$ axis due to the canting of $\mathrm{F}{\mathrm{e}}^{3+}$ magnetic moments. Around ${T}_{\mathrm{N}}$, the imaginary part of dielectric constant shows an anomaly. These results prove $h\ensuremath{-}\mathrm{ErFe}{\mathrm{O}}_{3}$ thin films to be multiferroic below 120 K.