XPS on Co<sub>0.95</sub>R<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub> Nanoparticles with R = Gd or Ho

XPS on Co<sub>0.95</sub>R<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub> Nanoparticles with R = Gd or Ho

Co<sub>0.95</sub>R<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub> nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic <i>Fd-3m</i> structure. XPS shows the pr...

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Main Authors: Adam Szatmari, Rareș Bortnic, Tiberiu Dragoiu, Radu George Hategan, Lucian Barbu-Tudoran, Coriolan Tiusan, Raluca Lucacel-Ciceo, Roxana Dudric, Romulus Tetean
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Applied Sciences
Subjects:
cobalt ferrite nanoparticles
heavy rare earths
cation distribution
XPS spectroscopy
magnetic properties
Online Access:https://www.mdpi.com/2076-3417/15/15/8313
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Summary:Co<sub>0.95</sub>R<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub> nanoparticles were synthesized using a sol-gel approach incorporating bio-based agents and were found to be single phases adopting a cubic <i>Fd-3m</i> structure. XPS shows the presence of Gd<sup>3+</sup> and Ho<sup>3+</sup> ions. The spin–orbit splitting of about 15.4 eV observed in Co 2<i>p</i> core-level spectra is an indication that Co is predominantly present as Co<sup>3+</sup> state, while the satellite structures located at about 6 eV higher energies than the main lines confirm the existence of divalent Co in Co<sub>0.95</sub>R<sub>0.05</sub>Fe<sub>2</sub>O<sub>4</sub>. The positions of the Co 3<i>s</i> and Fe 3<i>s</i> main peaks obtained by curve fitting and the exchange splitting obtained values for Co 3<i>s</i> and Fe 3<i>s</i> levels point to the high Co<sup>3+</sup>/Co<sup>2+</sup> and Fe<sup>3+</sup>/Fe<sup>2+</sup> ratios in both samples. The saturation magnetizations are smaller for the doped samples compared to the pristine ones. For theoretical magnetization calculation, we have considered that the heavy rare earths are in octahedral sites and their magnetic moments are aligned antiparallelly with 3d transition magnetic moments. ZFC-FC curves shows that some nanoparticles remain superparamagnetic, while the rest are ferrimagnetic, ordered at room temperature, and showing interparticle interactions. The <i>M</i><sub>S</sub>/<i>M</i>s ratio at room temperature is below 0.5, indicating the predominance of magnetostatic interactions.
ISSN:2076-3417

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