Sol-gel synthesis and the investigation of the properties of nanocrystalline holmium orthoferrite

Holmium orthoferrite nanocrystals (HoFeO$_3$) were synthesized from an aqueous solution by the sol-gel method, using polyvinyl alcohol as a stabilizer and annealing at temperatures of 650, 750, and 850$^\circ$C for an hour. According to the results of the performed analyses, it was found that with an increase in the annealing temperature, the average size of HoFeO$_3$ crystallites increases from 24 to 30 nm. The magnetic characteristics of the samples were measured and it was shown that holmium orthoferrite is a paramagnet with a low coercive force. The band gap of nanocrystalline holmium ferrite is determined.