Сrystal structure, valence state of ions and magnetic properties of HoFeO3 and HoFe0.8Sc0.2O3 nanoparticles from X-ray diffraction, X-ray photoelectron, and Mössbauer spectroscopy data

The HoFeO3 and HoFe0.8Sc0.2O3 nanoparticle samples were prepared by the solution combustion method using a mixture of fuels as carbamide and glucose. Their structural, electronic and magnetic properties are studied. The XRD study confirmed that the samples were single-phased and had Pbnm orthorhombic structure. The partial substitutions of Fe3+ ions by the Sc3+ ions with larger ionic radii resulted in the growth of lattice parameters. The surface morphology of the samples was examined by the scanning electron microscopy. The XPS data confirmed that both iron and scandium in the samples are trivalent. However, holmium was found to be trivalent only in the sample with a nominal composition HoFeO3. The data processing for the sample with a nominal composition of HoFe0.8Sc0.2O3 indicated that holmium ions were in Ho2+ and Ho3+ states with the ratio of 0.45/0.55. The Mossbauer study showed that iron ions in both samples were in Fe3+ state. About 10% of Fe3+ ions in HoFe0.8Sc0.2O3 were found to be in local environment with the coordination number 4. Collecting Mossbauer spectra in the temperature range of 14–723K allowed estimating magnetic phase transition temperatures (TM) for HoFeO3 and HoFe0.8Sc0.2O3 nanoparticle samples. TM values are 640K for HoFeO3 and 385K for HoFe0.8Sc0.2O3.