Room temperature multiferroic SmFeO3 thin films

Multiferroic materials have caught significant attention in the last decade because of its interesting properties and intriguing coupling between different order parameters. SmFeO₃ was predicted as a new type of room-temperature multiferroic system ever since 2012. It exhibits antiferromagnetism and significant magnetization below T_N ∼ 670 K. However, the existence of ferroelectricity of SmFeO₃ single crystal is still under debate. In this work, we process the growth of SmFeO₃ thin films on various single crystalline substrates, which has rarely been done hitherto. An elegant combination of multiple characterizations has been conducted to identify the ferroic natures of SmFeO₃ thin films. Atomic force microscopy is used to check the thin film surface, certifying the layer-by-layer growth nature. The interfacial strains are calculated by using high resolution XRD. X-ray absorption spectroscopy is used to determine the electronic structures. Piezoresponse force microscopy has clearly identified the ferroelectricity of SmFeO₃ grown on NdGaO₃ substrate. Furthermore, we processed first principle calculation to determine the origin of the ferroelectricity observed in the thin films. The information pileup reveals a new room temperature single-phase multiferroic system.