Structural, ferroelectric, and magnetic properties of epitaxial YMnO$_{3}$ thin films grown on wurtzite-structure materials

Thin films of the multiferroic oxide YMnO$_{3}$ have been grown on single crystal substrates with the wurtzite crystal structure, including GaN and ZnO with different polarities. Films have also been grown on the wurtzite derivative 6H-SiC. X-ray diffraction reveals epitaxial, c-axis oriented growth on all of these crystals. The measured ferroelectric polarization is similar to that of single crystal YMnO$_{3}$, and magnetization measurements reveal frustrated antiferromagnetic ordering in the plane of the film. X-ray diffraction also reveals an epitaxial relationship that is associated with a very large ($\sim $10{\%}) in-plane strain for growth on GaN. This unusual observation is explained by first principles calculations of the strain and bonding energies.