Hexagonal Lu_1-InFeO₃ Room-Temperature Multiferroic Thin Films

The hexagonal rare earth ferrites h-RFeO₃(R = rare earth element) have been recognized as promising candidates for a room-temperature multiferroic system, and the primary issue for these materials is how to get a stable hexagonal structure since the centrosymmetric orthorhombic structure is generally stable for most RFeO₃ at room-temperature, while the hexagonal phase is only stable under some strict conditions. In the present work, h-Lu_1-InFeO₃ (x = 0-1) thin films were prepared on a Nb-SrTiO₃ (111) single-crystal substrate by a pulsed laser deposition (PLD) process, and the multiferroic characterization was performed at room temperature. With the combined effects of chemical pressure and epitaxial strain, the stable hexagonal structure was achieved in a wide composition range (x = 0.5-0.7), and the results of XRD (X-ray diffraction) and SAED (selected area electron diffraction) indicate the super-cell match relations between the h-Lu_0.3In_0.7FeO₃ thin film and substrate. The saturated P-E hysteresis loop was obtained at room temperature with a remanent polarization of about 4.3 μC/cm², and polarization switching was also confirmed by PFM measurement. Furthermore, a strong magnetoelectric coupling with a linear magnetoelectric coefficient of 1.9 V/cm Oe was determined, which was about three orders of magnitude larger than that of h-RFeO₃ ceramics. The present results indicate that the h-Lu_1-InFeO₃ thin films are expected to have great application potential for magnetoelectric memory and detection devices.