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

Multiferroic materials exhibit multiple ferroic orders simultaneously and have potential applications in information technology. Hexagonal HoFeO$_{3}$ (h-HFO) is a promising candidate for a multiferroics with room temperature ferromagnetism because of the expected enhanced Fe moment due to the exchange interaction between magnetic Ho$^{3+}$ and Fe$^{3+}$ ions. We report study of magnetic properties of epitaxial (001) h-HFO thin films deposited on (111) yttria-stabilized zirconia substrates via laser molecular beam epitaxy. X-ray diffraction of h-HFO thin films shows a six-fold symmetry. X-ray magnetic circular dichroism (XMCD) spectra for the Fe L$_{2, 3}$ edges and Ho M$_{5}$ edge were measured with the magnetic field applied parallel to the x-ray propagation direction and 60$^{\circ}$ away from the film normal. Temperature dependence of the XMCD spectra shows ferromagnetic ordering of Fe$^{3+}$ ions up to 200 K and paramagnetic behavior for Ho$^{3+}$ ions above 10 K. The saturation magnetic moment for Fe$^{3+}$ is determined by the sum rules to be 0.26 $\mu_{B}$/Fe cation at 10 K and 0.064 $\mu_{B}$/Fe cation at 200 K, which is about 10 times larger than the reported saturation Fe$^{3+}$ magnetic moment in h-LuFeO$_{3}$. The SQUID magnetometer results agree with the XMCD results.