Electronic structure and magnetic anisotropies in orthorhombic multiferroic YMnO₃ thin films

Thermodynamically YMnO₃ (YMO) can only exist with hexagonal structure at ambient conditions. In this study, we demonstrate that the stain between film and substrate can play an important role in forming orthorhombic YMO (o-YMO). o-YMO films with nearly perfect crystallographic orientation alignment were obtained on LaAlO₃(110) substrates. These films allow us to unambiguously disclose the intrinsic magnetic property and electronic structure anisotropies along different crystallographic orientations. The antiferromagnetic (AFM) phase transition was around 42 K. Moreover, we observed a signature of spin reordering at lower temperatures when the applied field was parallel to the a- or c-axis. On the other hand, only the AFM transition was observed when the field is parallel to the b-axis. By comparing the X-ray absorption spectroscopy (XAS) results to standard manganese oxides, YMnO ₃ exhibits the dominant Mn⁺³ characteristics as that obtained from the standard Mn₂O₃ powder. The polarization dependent XAS also revealed anisotropic bonding behavior along each crystalline axis.