Morphology, structure and magnetic behavior of orthorhombic and hexagonal HoFeO3 synthesized via solution combustion approach

Nanostructured HoFeO3 powders were obtained by solution combustion method at various glycinenitrate ratios (G/N = 0.2, 0.4, ..., 1.4). According to X-ray powder diffractometry data, the presence of two modifications of HoFeO3 in the synthesized samples was established: orthorhombic (Pbnm) and hexagonal (P6(3)/mmc). The crystallite size of the obtained compositions varies from 62 +/- 6 to 29 +/- 3 nm, depending on the G/N ratio. From magnetic structure studies, it is found that HoFeO3 obtained with a stoichiometric amount of glycine in the reaction solution is in the magnetically ordered state and is represented by a sextet with quadrupole splitting (QS) = 0 mm/s, isomeric shift (IS) = 0.36 mm/s and effective field strength (H-eff) = 497 kOe. According to the results of vibrational magnetometry, it is found that the orthoferrites obtained have a ferromagnetic structure, the main parameters of which (M-s, M-r and H-c) systematically change with a change in the redox ratio of the reaction mixture and, as a consequence, their phase composition, and reach maximum values at a G/N ratio 1/4 0.6. In the samples obtained with a significant excess and lack of glycine (G/N = 0.2 and 1.4), despite their amorphous nature, hysteresis loops characteristic of the ferromagnetic state of the substance is observed. It is hopeful to obtain a pure hexagonal modification of HoFeO3 via heat treatment on amorphous products of glycine-nitrate combustion. (c) 2021 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.

Automated summary

Nanostructured HoFeO3 powders were synthesized by solution combustion method with different glycine-nitrate ratios. Two crystal structures, orthorhombic and hexagonal, were identified in the synthesized samples. The magnetic structure of HoFeO3 was found to be magnetically ordered in the presence of stoichiometric glycine. The size of the obtained compositions varied with the G/N ratio. The orthoferrites exhibited a ferromagnetic structure, and their magnetic parameters changed systematically with the redox ratio of the reaction mixture.