Structural studies and physical properties of hexagonal-YbFeO3 thin films

We present structural, magnetic, and optical properties of multiferroic hexagonal YbFeO3 thin films, deposited on single crystal (001) Al2O3 and (111) ysz substrates by a magnetron sputtering system. Interestingly, the thermal stress affects YbFeO3 films on Al2O3 and ysz very differently. Although hexagonal-YbFeO3/Al2O3 films changed from a hexagonal to an orthorhombic phase due to annealing above 1000 °C, hexagonal-YbFeO3/ysz films remained mostly unaffected even after annealing at 1200 °C. The electronic excitations of the YbFeO3 thin films are dominated by Fe3+ d to d on-site electronic excitations as well as O 2p to Fe 3d, Yb 6s, and 5d charge-transfer excitations, and these excitations for hexagonal-YbFeO3 and orthorhombic-YbFeO3 thin films are distinctly different, consistent with the crystal field environments in the hexagonal and orthorhombic phases of YbFeO3. The room temperature energy band gaps of the hexagonal-YbFeO3 and orthorhombic-YbFeO3 thin films were measured to be ∼1.95 ± 0.05 eV and ∼2.40 ± 0.05 eV, respectively.