Magnetic properties of epitaxial hexagonal HoFeO$_{3}$ thin films*

Multiferroic materials exhibit multiple ferroic orders simultaneously and thus have great potential applications in information technology, sensing and actuation. Epitaxial hexagonal HoFeO$_{3}$ (h-HFO) films are very promising candidates as multiferroic materials with room temperature ferromagnetism, because magnetic Ho$^{3+}$ ions are expected to have stronger exchange interactions with Fe$^{3+}$ ions than the well-studied h-LuFeO$_{3}$ films. We report study of magnetic properties of epitaxial h-HFO thin films deposited using laser molecular beam epitaxy on Yttria-stabilized zirconia (YSZ) substrates. X-ray diffraction measurements confirmed the epitaxial registry and six-fold symmetry of the film. Temperature dependence of magnetization of the film measured by a Quantum Design SQUID magnetometer shows dominating paramagnetic characteristic. Element specific x-ray magnetic circular dichroism measurements performed at beamline 4-ID-C of the Advanced Photon Source show a ferromagnetic ordering of Fe and an exchange coupling between Ho$^{3+}$ and Fe$^{3+}$ ions.