Origin of the magnetic transition at 100 K in ε-Fe2O3 nanoparticles studied by X-ray absorption fine structure spectroscopy

• Published in: Journal of physics. Condensed matter 2017-12, Vol.29 (48), p.485701-485701
• Main Authors: Sanchez, Jesus Lopez, Muñoz-Noval, Alvaro, Castellano, Carlo, Serrano, Aida, Del Campo, Adolfo, Cabero, Mariona, Varela, Maria, Abuín, Manuel, de la Figuera, Juan, Marco, José F, Castro, German R, Rodriguez de la Fuente, Oscar, Carmona, Noemi
• Format: Article
• Language: English
• ISSN: 1361-648X
• DOI: 10.1088/1361-648X/aa904b

We present a study of the correlation between the magnetic phase transition and the structural distortion observed at 100 K in ε-Fe2O3. For this purpose, we have designed a novel one-pot sol-gel method assisted by glycerol, which reproducibly provides samples with a nominal 100% concentration of ε-Fe2O3 nanoparticles embedded in a SiO2 matrix. The high crystallinity of the samples and the absence of other iron oxide polymorphs has allowed us to perform, for the first time, temperature-dependent X-ray absorption fine structure spectroscopy experiments, with the aim of investigating the origin of the magnetic quenching anomaly observed at 100 K. The deformation of the structure at a local scale, where the tetrahedral and octahedral Fe sites undergo distortions of different intensities, has been simulated to fulfill the long-range order. Our results point to a local structure distortion accompanied by the magnetism quenching through a magneto-elastic coupling.